feat(interrupts): query last serviced interrupt

This patch introduces a helper API to request Cactus SP to return the
ID of the last serviced secure virtual interrupt. It is built on cactus
command framework by leveraging direct message request and response
pair.

Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
Change-Id: I316268f4d9b80f29c308d1a1488945a272ffbc93
3 files changed