refactor(interrupts): enhance secure interrupt handling test

This test makes sure SPMC was able to handle back-to-back
secure interrupts targetting Cactus SP while the SP was in
RUNNING state.

Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
Change-Id: If2e93017e2c21ad91fe527fb140f0fd5e0252370
3 files changed