fix(lib): declare unused parameters as void

This corrects the MISRA violation C2012-2.7:
There should be no unused parameters in functions.
Declared unused function parameters as void.

Change-Id: I979ba118fd209be5d4f0bff3978479c22428d79b
Signed-off-by: Nithin G <nithing@amd.com>
Signed-off-by: Maheedhar Bollapalli <maheedharsai.bollapalli@amd.com>
diff --git a/lib/psci/psci_main.c b/lib/psci/psci_main.c
index 308c6f9..4799fc6 100644
--- a/lib/psci/psci_main.c
+++ b/lib/psci/psci_main.c
@@ -445,6 +445,9 @@
 			  void *handle,
 			  u_register_t flags)
 {
+	(void)x4;
+	(void)cookie;
+	(void)handle;
 	u_register_t ret;
 
 	if (is_caller_secure(flags)) {