rtc: max77686: add Maxim 77686 driver

rtc: max77686: add Maxim 77686 driver

Add a driver to support max77686 rtc.  MAX77686 rtc support smpl and wtsr
mode.  It has two alarm register which can be used for alarming to wake
system up.  This drvier uses regmap to access its register.

Signed-off-by: Chiwoong Byun <woong.byun@samsung.com>
Signed-off-by: Jonghwa Lee <jonghwa3.lee@samsung.com>
Signed-off-by: Myugnjoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>