feat(interrupts): discover interrupt ID of managed exit signal

Added support for discovering managed exit interrupt ID in Cactus SP
using FFA_FEATURES ABI during partition initialization.

Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
Change-Id: I0b6ea04fc18d6903d821e2f890e4e0a4ad5d568a
3 files changed