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: NDmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: NAlessandro Zummo <a.zummo@towertech.it>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-ds1307.c

@@ -874,7 +874,7 @@ static int __devinit ds1307_probe(struct i2c_client *client,
 	}
 
 	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,