rtc: rtc-sh: Fix up oops in early periodic freq assignment.

With the reordered init order, the rtc device is not registered until
later, while sh_rtc_irq_set_freq() was attempting to assign ->irq_freq
directly, resulting in an oops. This is handled by the upper layers for
us, so just kill off the problematic dereference completely.
Reported-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

drivers/rtc/rtc-sh.c

@@ -283,10 +283,8 @@ static int sh_rtc_irq_set_freq(struct device *dev, int freq)
 		ret = -ENOTSUPP;
 	}
 
-	if (ret == 0) {
+	if (ret == 0)
 		rtc->periodic_freq |= tmp;
-		rtc->rtc_dev->irq_freq = freq;
-	}
 
 	spin_unlock_irq(&rtc->lock);
 	return ret;