selftests/timers: Remove unused NSEC_PER_SEC macro

By reading the code, I found the macro NSEC_PER_SEC
is never referenced in the code. Just remove it.
Signed-off-by: zhang jiao <zhangjiao2@cmss.chinamobile.com>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: John Stultz <jstultz@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/timers/change_skew.c

@@ -30,9 +30,6 @@
 #include <time.h>
 #include "../kselftest.h"
 
-#define NSEC_PER_SEC 1000000000LL
-
-
 int change_skew_test(int ppm)
 {
 	struct timex tx;

tools/testing/selftests/timers/skew_consistency.c

@@ -36,8 +36,6 @@
 #include <sys/wait.h>
 #include "../kselftest.h"
 
-#define NSEC_PER_SEC 1000000000LL
-
 int main(int argc, char **argv)
 {
 	struct timex tx;