selftests: vDSO: vdso_test_abi: Use explicit indices for name array

The array relies on the numeric values of the clock IDs.
When reading the code it is not obvious that the order is correct.

Make the code easier to read by using explicit indices.

While at it make the array static.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250812-vdso-tests-fixes-v2-5-90f499dd35f8@linutronix.de

Author: t-8ch

tools/testing/selftests/vDSO/vdso_test_abi.c

@@ -31,19 +31,19 @@ typedef long (*vdso_clock_gettime_t)(clockid_t clk_id, struct timespec *ts);
 typedef long (*vdso_clock_getres_t)(clockid_t clk_id, struct timespec *ts);
 typedef time_t (*vdso_time_t)(time_t *t);
 
-const char *vdso_clock_name[12] = {
-	"CLOCK_REALTIME",
-	"CLOCK_MONOTONIC",
-	"CLOCK_PROCESS_CPUTIME_ID",
-	"CLOCK_THREAD_CPUTIME_ID",
-	"CLOCK_MONOTONIC_RAW",
-	"CLOCK_REALTIME_COARSE",
-	"CLOCK_MONOTONIC_COARSE",
-	"CLOCK_BOOTTIME",
-	"CLOCK_REALTIME_ALARM",
-	"CLOCK_BOOTTIME_ALARM",
-	"CLOCK_SGI_CYCLE",
-	"CLOCK_TAI",
+static const char * const vdso_clock_name[] = {
+	[CLOCK_REALTIME]		= "CLOCK_REALTIME",
+	[CLOCK_MONOTONIC]		= "CLOCK_MONOTONIC",
+	[CLOCK_PROCESS_CPUTIME_ID]	= "CLOCK_PROCESS_CPUTIME_ID",
+	[CLOCK_THREAD_CPUTIME_ID]	= "CLOCK_THREAD_CPUTIME_ID",
+	[CLOCK_MONOTONIC_RAW]		= "CLOCK_MONOTONIC_RAW",
+	[CLOCK_REALTIME_COARSE]		= "CLOCK_REALTIME_COARSE",
+	[CLOCK_MONOTONIC_COARSE]	= "CLOCK_MONOTONIC_COARSE",
+	[CLOCK_BOOTTIME]		= "CLOCK_BOOTTIME",
+	[CLOCK_REALTIME_ALARM]		= "CLOCK_REALTIME_ALARM",
+	[CLOCK_BOOTTIME_ALARM]		= "CLOCK_BOOTTIME_ALARM",
+	[10 /* CLOCK_SGI_CYCLE */]	= "CLOCK_SGI_CYCLE",
+	[CLOCK_TAI]			= "CLOCK_TAI",
 };
 
 static void vdso_test_gettimeofday(void)