Rename SMC first argument

'fid' (short for 'function ID') makes for a more explicit name.

Change-Id: I41d90c39979162142b0377a68f4be90dc31de253
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
diff --git a/tftf/tests/performance_tests/smc_latencies.c b/tftf/tests/performance_tests/smc_latencies.c
index fe22679..49733cf 100644
--- a/tftf/tests/performance_tests/smc_latencies.c
+++ b/tftf/tests/performance_tests/smc_latencies.c
@@ -143,7 +143,7 @@
 	/* Check if SMCCC version is at least v1.1 */
 	expected_ver = MAKE_SMCCC_VERSION(1, 1);
 	memset(&args, 0, sizeof(args));
-	args.arg0 = SMCCC_VERSION;
+	args.fid = SMCCC_VERSION;
 	ret = tftf_smc(&args);
 	if ((int32_t)ret.ret0 < expected_ver) {
 		printf("Unexpected SMCCC version: 0x%x\n",
@@ -153,7 +153,7 @@
 
 	/* Check if SMCCC_ARCH_WORKAROUND_1 is implemented */
 	memset(&args, 0, sizeof(args));
-	args.arg0 = SMCCC_ARCH_FEATURES;
+	args.fid = SMCCC_ARCH_FEATURES;
 	args.arg1 = SMCCC_ARCH_WORKAROUND_1;
 	ret = tftf_smc(&args);
 	if ((int)ret.ret0 == -1) {
@@ -162,7 +162,7 @@
 	}
 
 	memset(&args, 0, sizeof(args));
-	args.arg0 = SMCCC_ARCH_WORKAROUND_1;
+	args.fid = SMCCC_ARCH_WORKAROUND_1;
 
 	test_measure_smc_latency(&args, &latency);
 	tftf_testcase_printf(