SAMV7: Quick'n'dirty port of the SAMA5D4 Ethernet MAC driver to the SAMV7.  Still some unresovled issues with DCache handling

This commit enables HSMCI functionality in the SAMV71-XULT.  TX DMA is, unfortunately, currently disabled.

SAMA5:  Fix a bug in SAMA5 HSMCI.  The bitfield mask and shift values were reversed resulting in a trashed value for the number of blocks in the BLOCKR register.  This was sufficient to prevent DMA writes from working.

SAMV71: Quick'n'dirty port of the SAMA5 SSC driver to the SAM7.  The IP is compatible but there are still some DMA- and Cache-related issues that need to be worked out.

mq_timedsend():  Do check for time errors if the message queue is not full.  Noted by Freddie Chopin

SAMV7:  Update floating point and TCM configuration options.  Update TODO list.  Update comments.  Refresh a configuration

SAMV71-XULT: Add support for on-board LEDs.  Includes partial support for on-board buttons.  Some corrections fo to egg-stk37000 and sam4e-ek discovered during leveraging.  Add board READEM.txt file