Squashed commit of the following:

commit 91e985a87729017a66d19276c4d47681064f95ea
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Tue Jul 25 15:13:54 2017 -0600

    Spirit:  Add a few more functions that will soon be needed for packet transmission.

commit b5981d29983907c2194fbc26af4b72ad532bee78
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Tue Jul 25 13:30:07 2017 -0600

    Spirit:  Finish off some initialization issues; Started some interrupt handling logic.

commit c21073e0bc2870b3d9ba40bdfdfd5151ce4f5890
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Tue Jul 25 09:35:52 2017 -0600

    Spirit:  Completes very basic radio initialization for network driver

commit 1b544334361c54f46bcf0ba313c125932e8dafc6
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Tue Jul 25 07:58:30 2017 -0600

    Spirit: Add more radio initialization logic... getting closer.

commit 45d1047db60843c57d394ec910c63e7c127671e0
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Mon Jul 24 19:15:33 2017 -0600

    Spirit: add some CSMA initialization logic

commit bcf55c71336d48947fe19bb09a799169852301c2
Merge: 89e9d426e9 2fc0fbcf
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Mon Jul 24 16:47:11 2017 -0600

    Merge remote-tracking branch 'origin/master' into spirit

commit 89e9d426e91c056e659fccf5e5c4392618f8f777
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Mon Jul 24 16:44:19 2017 -0600

    Update some comments

commit 9c5d8a5833350006ed389e898b11c8c8a20e5f4f
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Mon Jul 24 16:15:54 2017 -0600

    Spirit:  Rename drivers/wireless/spirit/src to lib.  Move Spirit network driver out of IEEE802.15.4 into drivers/wireless/spirit/drivers

commit cabc0ec9e6eb558dcb715ab17264383aa0105e7a
Merge: 87b616414a 6bd744c4
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Mon Jul 24 15:38:40 2017 -0600

    Merge remote-tracking branch 'origin/master' into spirit

commit 87b616414a79c01a71acea78f8258e05325c1996
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Mon Jul 24 15:37:27 2017 -0600

    Spirit radio driver is mutating into a standalone network driver.

commit 507798233868a661ae8adad3e3aa117075a7a146
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Mon Jul 24 13:32:08 2017 -0600

    Spirit: More radio initialization logic

commit 33af25704ce9ca83d576300d153cfe31cc6d2576
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Mon Jul 24 12:19:14 2017 -0600

    Spirit:  Beginning of radio initialization logic

commit 97b20014c016e55952a8f9d8f4ae29e2cc555b23
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Mon Jul 24 09:42:06 2017 -0600

    Spirit: More initialization logic.

commit 295d8e27824c0417fccea2344b30bb5c93ffbabe
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sun Jul 23 15:39:53 2017 -0600

    Spirit:  Add header file containing enumeration of commands.

commit 8a2d9dd8eb9cc70cbcdd1b913fc9022b9c9ec8da
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sun Jul 23 11:33:50 2017 -0600

    Spirit:  Add GPIO initialization logic

commit 8b6d80c44f92024c45a6ba63ba1af3fdafe94dc3
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sun Jul 23 10:07:25 2017 -0600

    Spirit:  Add interrupt control logic.

commit 423f846fe5c914f92a4bfea4d9d1fa33de1c77a5
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sat Jul 22 19:06:52 2017 -0600

    Spirit: Yet a little more radio initialization logic.

commit 5895b979823e51ddde5ad52e6de66a8ad662e883
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sat Jul 22 15:36:05 2017 -0600

    Spirit: A little more radio initialization logic.

commit 86311ab30aad386203c181c792847dd1d37f9a02
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sat Jul 22 13:02:32 2017 -0600

    Spirit: A miniscule amount of radio initialization logic.

commit ad55e89d5ee12ea1eeea95fcd38ff3da0db4416a
Merge: 90a7666655 f4e46b0d
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sat Jul 22 10:56:30 2017 -0600

    Merge remote-tracking branch 'origin/master' into spirit

commit 90a766665534b05da0157dbc383cb06a98c86a79
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sat Jul 22 10:52:52 2017 -0600

    Spirit1:  A few fixes for a clean build of initial configuration (not much there yet)

commit bbbf04c223230a52a7705a2161128265cfbaa480
Merge: 623d54a7f7 2319ea53
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sat Jul 22 09:53:57 2017 -0600

    Merge remote-tracking branch 'origin/master' into spirit

commit 623d54a7f719e9032099f88f38203efee4b80722
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sat Jul 22 09:43:52 2017 -0600

    b-l475e-iot01a: Add a configuration for testing sprit radio.

commit d309d73d9f4665f9d870eb03531f450043d9389d
Merge: 52c3ddfae6 d88dc9b2
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sat Jul 22 09:02:06 2017 -0600

    Merge remote-tracking branch 'origin/master' into spirit

commit 52c3ddfae6802e111c2b5cf1207baf21a61dd00b
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sat Jul 22 08:33:04 2017 -0600

    Spirit:  Add register definition header file.

commit 8d842ab5e8f9ca653b42f9ee88dc279f06b4fa98
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Fri Jul 21 17:27:03 2017 -0600

    b-l475e-iot01a: Add initial, unverified support for the SPSRGF/Spirit1 module.

commit 73d902a1048616fb9c2dd2147cabcd8ee78e19ac
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Fri Jul 21 15:49:43 2017 -0600

    Spirit: Fixes to get skeleton IEEE 802.15.4 driver build.

commit ebc5a8387bb94f0cc3827533795f3e4a33207e67
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Fri Jul 21 15:16:29 2017 -0600

    Spirit1:  Add framework for IEEE 802.15.4 driver.  Does not yet build.

commit 52e195a7ae14ddb18bdd56258f4877381d2501ca
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Fri Jul 21 14:02:42 2017 -0600

    Spirit:  A little more SPI logic.

commit 90048d0c5b8a5af4d81a15d99535c84ed38d8ae9
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Fri Jul 21 11:19:06 2017 -0600

    Spirit: Build directories setup.  Some initial files added, mostly just to verify build.

commit 8273a381ac1f6bb081b292b5e73226185e9e634c
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Fri Jul 21 08:34:04 2017 -0600

    USB composite:  Remove references to CDC/ACM and USB MSC from composite logic.  They are no longer coupled.