refactor: create vcpu_secure_interrupt_complete

Created the function vcpu_secure_interrupt_complete as a direct
replacement to plat_ffa_reset_secure_interrupt_flags.

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: I416c81c516dc8f3f6ea1b73de21424e4b7dc4d09
diff --git a/src/vcpu.c b/src/vcpu.c
index 5336052..b5f0d2f 100644
--- a/src/vcpu.c
+++ b/src/vcpu.c
@@ -506,3 +506,16 @@
 
 	return false;
 }
+
+/**
+ * When interrupt handling is complete the preempted_vcpu field should go back
+ * to NULL.
+ */
+void vcpu_secure_interrupt_complete(struct vcpu_locked vcpu_locked)
+{
+	struct vcpu *vcpu;
+
+	vcpu = vcpu_locked.vcpu;
+	vcpu->preempted_vcpu = NULL;
+	vcpu->implicit_completion_signal = false;
+}