selftests/breakpoints:Remove unused variable

This variable is never referenced in the code, just remove them
that this problem was discovered by reading the code
Signed-off-by: Zhu Jun <zhujun2@cmss.chinamobile.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/breakpoints/step_after_suspend_test.c

@@ -130,7 +130,6 @@ int run_test(int cpu)
 void suspend(void)
 {
 	int power_state_fd;
-	struct sigevent event = {};
 	int timerfd;
 	int err;
 	struct itimerspec spec = {};