selftests/vDSO: fix array_size.cocci warning

Fix the following coccicheck warning:

tools/testing/selftests/vDSO/vdso_test_correctness.c:309:46-47:
WARNING: Use ARRAY_SIZE
tools/testing/selftests/vDSO/vdso_test_correctness.c:373:46-47:
WARNING: Use ARRAY_SIZE

It has been tested with gcc (Debian 8.3.0-6) 8.3.0 on x86_64.
Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/vDSO/vdso_test_correctness.c

@@ -20,6 +20,7 @@
 #include <limits.h>
 
 #include "vdso_config.h"
+#include "../kselftest.h"
 
 static const char **name;
 
@@ -306,10 +307,8 @@ static void test_clock_gettime(void)
 		return;
 	}
 
-	for (int clock = 0; clock < sizeof(clocknames) / sizeof(clocknames[0]);
-	     clock++) {
+	for (int clock = 0; clock < ARRAY_SIZE(clocknames); clock++)
 		test_one_clock_gettime(clock, clocknames[clock]);
-	}
 
 	/* Also test some invalid clock ids */
 	test_one_clock_gettime(-1, "invalid");
@@ -370,10 +369,8 @@ static void test_clock_gettime64(void)
 		return;
 	}
 
-	for (int clock = 0; clock < sizeof(clocknames) / sizeof(clocknames[0]);
-	     clock++) {
+	for (int clock = 0; clock < ARRAY_SIZE(clocknames); clock++)
 		test_one_clock_gettime64(clock, clocknames[clock]);
-	}
 
 	/* Also test some invalid clock ids */
 	test_one_clock_gettime64(-1, "invalid");