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
diff --git a/spm/common/sp_helpers.h b/spm/common/sp_helpers.h
index ef60221..98af484 100644
--- a/spm/common/sp_helpers.h
+++ b/spm/common/sp_helpers.h
@@ -78,4 +78,6 @@
 /* Un-register the handler. */
 void sp_unregister_interrupt_tail_end_handler(uint32_t interrupt_id);
 
+void discover_managed_exit_interrupt_id(void);
+
 #endif /* SP_HELPERS_H */