rtc: rtctest: Change no IRQ detection for RTC_IRQP_SET

A call to ioctl(..., RTC_IRQP_SET, ...) 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

@@ -218,7 +218,7 @@ int main(int argc, char **argv)
 		retval = ioctl(fd, RTC_IRQP_SET, tmp);
 		if (retval == -1) {
 			/* not all RTCs can change their periodic IRQ rate */
-			if (errno == ENOTTY) {
+			if (errno == EINVAL) {
 				fprintf(stderr,
 					"\n...Periodic IRQ rate is fixed\n");
 				goto done;