SPM: Clear 'signals_waiting' when partition wakes up

When a partition wakes up, it does not wait for any signals
at the moment. This patch sets the 'signals_waiting' to 0
when a partition wakes up. The 'signals_waiting' will be set
again when the partition calls 'psa_wait()' the next time.

Signed-off-by: Mingyang Sun <mingyang.sun@arm.com>
Change-Id: Ia57079206d6d0d764756e048fb8f3a2b68c869f3
diff --git a/secure_fw/spm/ffm/backend_ipc.c b/secure_fw/spm/ffm/backend_ipc.c
index 11a4235..f778831 100644
--- a/secure_fw/spm/ffm/backend_ipc.c
+++ b/secure_fw/spm/ffm/backend_ipc.c
@@ -226,11 +226,11 @@
     return ret_signal;
 }
 
-static void ipc_wake_up(struct partition_t *p_pt, psa_signal_t signals)
+static void ipc_wake_up(struct partition_t *p_pt)
 {
     thrd_wake_up(&p_pt->waitobj,
                  p_pt->signals_asserted & p_pt->signals_waiting);
-    p_pt->signals_waiting &= ~signals;
+    p_pt->signals_waiting = 0;
 }
 
 const struct backend_ops_t backend_instance = {