feat(ras): move wait logic from assembley to C

SDEI test uses a flag to be updated through SDEI handler to ensure that
test has passed, this logic was implemented in assembly, move this logic
in C to make it easily readable.

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: I4c92aa7a6fbeb5fcdb4c67b0166627a539609f18
2 files changed