selftests: timers: drop support for !KTEST case

There is no need to keep timers tests in sync with external timers
repo. Drop support for !KTEST to support for building and running
timers tests without kselftest framework.

Reference: https://lkml.org/lkml/2017/8/10/952
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Acked-by: John Stultz <john.stultz@linaro.org>

tools/testing/selftests/timers/threadtest.c

@@ -21,19 +21,7 @@
 #include <stdlib.h>
 #include <sys/time.h>
 #include <pthread.h>
-#ifdef KTEST
 #include "../kselftest.h"
-#else
-static inline int ksft_exit_pass(void)
-{
-	exit(0);
-}
-static inline int ksft_exit_fail(void)
-{
-	exit(1);
-}
-#endif
-
 
 /* serializes shared list access */
 pthread_mutex_t list_lock = PTHREAD_MUTEX_INITIALIZER;