Platform: Reduce SPM's stack size on Musca A1

Set SPM's stack size to 0x1000 due two reason:
 - be aligned with other targets
 - fit to 64KB RAM

Change-Id: I30d4cc9673e11f745287fc3725f56f86f2aef85b
Signed-off-by: Tamas Ban <tamas.ban@arm.com>
3 files changed