drivers/rtc/rtc-max77686.c: Fix wrong register

commit 1748cbf7f7c464593232cde914f5a103181a83b5 upstream.

Fix a read of the wrong register when checking whether the RTC timer has
reached the alarm time.

Signed-off-by: Sangjung Woo <sangjung.woo@samsung.com>
Signed-off-by: Myugnjoo Ham <myungjoo.ham@samsung.com>
Reviewed-by: Jonghwa Lee <jonghwa3.lee@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jonghwan Choi <jhbird.choi@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>