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.

[[email protected]: remove inline, __devinit annotations]
[[email protected]: fix build warnings]
[[email protected]: simplify code]
Signed-off-by: Chiwoong Byun <[email protected]>
Signed-off-by: Jonghwa Lee <[email protected]>
Signed-off-by: Myugnjoo Ham <[email protected]>
Signed-off-by: Kyungmin Park <[email protected]>
Signed-off-by: Jingoo Han <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>