rtc: ds1307 make it possible to share an irq

It's possible to have RTC irq shared with other device (e.g.
mpc8349e-mitx board shares ds1339 irq with phy one).  Handle this in
driver.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-ds1307.c

@@ -874,7 +874,7 @@ read_rtc:
 	}
 
 	if (want_irq) {
-		err = request_irq(client->irq, ds1307_irq, 0,
+		err = request_irq(client->irq, ds1307_irq, IRQF_SHARED,
 			  ds1307->rtc->name, client);
 		if (err) {
 			dev_err(&client->dev,