feat(rme): add PMU Realm tests

This patch adds Realm PMU payload tests with
PMU interrupt handling.

Signed-off-by: AlexeiFedorov <Alexei.Fedorov@arm.com>
Change-Id: I86ef96252e04c57db385e129227cc0d7dcd1fec2
diff --git a/tftf/tests/common/test_helpers.c b/tftf/tests/common/test_helpers.c
index cba4dad..90773ae 100644
--- a/tftf/tests/common/test_helpers.c
+++ b/tftf/tests/common/test_helpers.c
@@ -1,9 +1,11 @@
 /*
- * Copyright (c) 2020-2022, Arm Limited. All rights reserved.
+ * Copyright (c) 2020-2023, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
+#include <stdlib.h>
+
 #include <arch_helpers.h>
 #include <cactus_test_cmds.h>
 #include <plat_topology.h>
@@ -270,3 +272,9 @@
 		continue;
 	}
 }
+
+/* Generate 64-bit random number */
+unsigned long long rand64(void)
+{
+	return ((unsigned long long)rand() << 32) | rand();
+}