rtc: rtctest: Change no IRQ detection for RTC_IRQP_READ

A call to ioctl(..., RTC_IRQP_READ, ...) should never result in
ENOTTY. All new style RTC drivers implement it and all of the old style
drivers return EINVAL when they don't support periodic IRQs.
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

tools/testing/selftests/timers/rtctest.c

@@ -200,7 +200,7 @@ int main(int argc, char **argv)
 	retval = ioctl(fd, RTC_IRQP_READ, &tmp);
 	if (retval == -1) {
 		/* not all RTCs support periodic IRQs */
-		if (errno == ENOTTY) {
+		if (errno == EINVAL) {
 			fprintf(stderr, "\nNo periodic IRQ support\n");
 			goto done;
 		}