selftests: timers: improve timer_create failure message

improve timer_create failure message with strerror() function
to give more information to the user.

Signed-off-by: Gianfranco Trad <[e-mail]>
Acked-by: John Stultz <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

tools/testing/selftests/timers/alarmtimer-suspend.c

···
 #include <stdlib.h>
 #include <pthread.h>
 #include <include/vdso/time64.h>
+#include <errno.h>
 #include "../kselftest.h"
 
 #define CLOCK_REALTIME			0
···
 
 		alarmcount = 0;
 		if (timer_create(alarm_clock_id, &se, &tm1) == -1) {
-			printf("timer_create failed, %s unsupported?\n",
-					clockstring(alarm_clock_id));
+			printf("timer_create failed, %s unsupported?: %s\n",
+					clockstring(alarm_clock_id), strerror(errno));
 			break;
 		}