feat(notifications): get notifications from SPs

Handling the call FFA_NOTIFICATION_GET to retrieve pending notifications
from SPs:
- SPMC retrieves the pending notifications from the partition's bitmap
field;
- Hypervisor forwards the call to SPMC, analyzes the returned value
and populates its return to the VM.
Hypervisor case useful to test notifications full signaling flow from
NWd.

Change-Id: Icda45d0bca025a023c75ec2ceecf15d06c2456a0
Signed-off-by: J-Alves <joao.alves@arm.com>
diff --git a/src/api.c b/src/api.c
index 37a6ca9..27189e9 100644
--- a/src/api.c
+++ b/src/api.c
@@ -2809,12 +2809,12 @@
 	}
 
 	if ((flags & FFA_NOTIFICATION_FLAG_BITMAP_SP) != 0U) {
-		/*
-		 * TODO: For hypervisor, forward call to SPMC to get VM's
-		 * notifications from SPs.
-		 */
-		sp_notifications = vm_notifications_get_pending_and_clear(
-			receiver_locked, false, vcpu_id);
+		if (!plat_ffa_notifications_get_from_sp(
+			    receiver_locked, vcpu_id, &sp_notifications,
+			    &ret)) {
+			dlog_verbose("Failed to get notifications from sps.");
+			goto out;
+		}
 	}
 
 	if ((flags & FFA_NOTIFICATION_FLAG_BITMAP_VM) != 0U) {