Platform: Add GNUARM support for Musca platform

Details:
 - add necessary startup files and linker scripts
 - update platform/ext/musca_a.cmake
 - fix region_defs.h syntax to be compatible with the linker
 - add special 4 byte aligned memset and memcpy functions to flash
   driver

Change-Id: I2339abeff1f0187053d39c1f000bf95c7f8a200f
Signed-off-by: Mate Toth-Pal <mate.toth-pal@arm.com>
17 files changed