cactus: implement hvc call to get interrupt id

Since an SP cannot access GIC directly, it relies on SPMC(S-EL2) to
get the interrupt ID.
This patch introduces a new hvc call "SPM_INTERRUPT_GET" to get
interrupt ID in S-EL1.

Change-Id: I37626f907174ae57a24dc6b86e89d26ba8ebbddf
Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
3 files changed