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>
diff --git a/include/runtime_services/ffa_helpers.h b/include/runtime_services/ffa_helpers.h
index 197879e..2cc2c46 100644
--- a/include/runtime_services/ffa_helpers.h
+++ b/include/runtime_services/ffa_helpers.h
@@ -23,6 +23,7 @@
 typedef unsigned short ffa_vm_id_t;
 typedef unsigned short ffa_vm_count_t;
 typedef unsigned short ffa_vcpu_count_t;
+typedef uint32_t ffa_int_id_t;
 
 #ifndef __ASSEMBLY__