Add tests for MTE support

TF-A now has support for the new Memory Tagging Extension in ARMv8.5,
see commit 91624b7fed52 ("Merge changes from topic "jc/mte_enable"
into integration").

This patch creates and enables tests to ensure that the extension is
being properly enabled and that no undesired leakages occur.

Change-Id: I7708fb23a12e2f35a97533f296aaa53db776ddd2
Signed-off-by: Justin Chadwell <justin.chadwell@arm.com>
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
diff --git a/include/common/test_helpers.h b/include/common/test_helpers.h
index 141f00c..77cf7fd 100644
--- a/include/common/test_helpers.h
+++ b/include/common/test_helpers.h
@@ -109,6 +109,15 @@
 		}								\
 	} while (0)
 
+#define SKIP_TEST_IF_MTE_SUPPORT_LESS_THAN(n)					\
+	do {									\
+		if (get_armv8_5_mte_support() < (n)) {				\
+			tftf_testcase_printf(					\
+				"Memory Tagging Extension not supported\n");	\
+			return TEST_RESULT_SKIPPED;				\
+		}								\
+	} while (0)
+
 #define SKIP_TEST_IF_MM_VERSION_LESS_THAN(major, minor)				\
 	do {									\
 		smc_args version_smc = { MM_VERSION_AARCH32 };			\