rtc: make example code jump to done instead of return when ioctl not supported

Signed-off-by: Hans-Christian Egtvedt <[e-mail]>
Cc: Haavard Skinnemoen <[e-mail]>
Cc: David Brownell <[e-mail]>
Cc: Alessandro Zummo <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/rtc.txt

···
 		/* not all RTCs support periodic IRQs */
 		if (errno == ENOTTY) {
 			fprintf(stderr, "\nNo periodic IRQ support\n");
-			return 0;
+			goto done;
 		}
 		perror("RTC_IRQP_READ ioctl");
 		exit(errno);