selftests/timers: Add missing error code assignment before test

In order to work, the 'err' return value has to be updated otherwise the
test can never be true.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/timers/posix_timers.c

@@ -122,7 +122,7 @@ static int check_itimer(int which)
 	else if (which == ITIMER_REAL)
 		idle_loop();
 
-	gettimeofday(&end, NULL);
+	err = gettimeofday(&end, NULL);
 	if (err < 0) {
 		perror("Can't call gettimeofday()\n");
 		return -1;
@@ -175,7 +175,7 @@ static int check_timer_create(int which)
 
 	user_loop();
 
-	gettimeofday(&end, NULL);
+	err = gettimeofday(&end, NULL);
 	if (err < 0) {
 		perror("Can't call gettimeofday()\n");
 		return -1;