rtc: s5m: add support for S2MPS14 RTC

Add support for S2MPS14 to the rtc-s5m driver.  Differences in S2MPS14
(in comparison to S5M8767):

 - Layout of registers
 - Lack of century support for time and alarms (7 registers used for
   storing time/alarm)
 - Two buffer control registers: WUDR and RUDR
 - No register for enabling writing time
 - RTC interrupts are reported in main PMIC I2C device

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Sangbeom Kim <sbkim73@samsung.com>
Cc: Samuel Ortiz <sameo@linux.intel.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>