staging: android-alarm: Update hrtimer if alarm at the head of the queue is reprogrammed

If an alarm was restarted with a value that moved it away from the head
of a queue, the hrtimer would not be updated. This would cause unnecessary
wakeups.

CC: Arve Hjønnevåg <arve@android.com>
CC: Android Kernel Team <kernel-team@android.com>
Signed-off-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Change-Id: If379f8dd92b0bdb3173bd8d057adfe0dc1d15259