On receiving CPU power down callback, TF-A raises SGI interrupt to all active
cores to power down each active cores. Add handler for this SGI IRQ.
By default TF-A uses SGI 6 for CPU power down request. This can be
configurable through CPU_PWRDWN_SGI build flag.
e.g., If user wants to use SGI 7 instead of SGI 6 then provide build
flag CPU_PWRDWN_SGI=7
Signed-off-by: Jay Buddhabhatti <jay.buddhabhatti@amd.com>
Change-Id: Id0df32187d1de3f0af4486eb4d4930cb3ab01dbd
ade92a64e4