wireless/ieee802154: Lots of little fixes and changes to get everything to build

Approved-by: Gregory Nutt <gnutt@nuttx.org>

configs: Remove all setenv.bat files.  Remove all references to setenv.sh and setenv.bat from all config README files.

CONFIG_DEBUG_HARDFAULT should be available for Cortex-M0 too.  configs/nucle-f072rb/nsh: Correct amount of available SRAM in defconfig.

procfs: Fix incorrect uptime with CONFIG_SYSTEM_TIME64

Jira: PDFW15IS-45
Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

sched: Fix CHILD_FLAG_EXITED in include/nuttx/sched.h

Approved-by: Gregory Nutt <gnutt@nuttx.org>

Jira: PDFW15IS-196
Jira: PDFW15IS-1109
Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

USBMSC: Fix a wrong lun number issue

Approved-by: Gregory Nutt <gnutt@nuttx.org>

Jira: PDFW15IS-98
Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

net: network drver now retains Ethernet MAC address in a union so that other link layer addresses may be used in a MULTILINK environment.

6loWPAN: Remove the PAN ID from the 6loWPAN data structure.  This is owned by the radio driver.  Rather, use an IOCTL to obtain the PAN ID from the downstream radio driver.