drivers/rtc/mxc: Modify rtc_update_alarm() not to touch the alarm time

rtc_class_ops's set_alarm() shouldn't deal with the alarm date,
as this is handled in the rtc core.

See rtc_dev_ioctl()'s RTC_ALM_SET and RTC_WKALM_SET cases.

Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1427945681-29972-12-git-send-email-john.stultz@linaro.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>