mfd: sec-core: Add support for S2MPS13 device

This patch adds the support for Samsung S2MPS13 PMIC device to the sec-core MFD
driver. The S2MPS13 is very similar with existing S2MPS14 and includes PMIC/
RTC/CLOCK devices.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Sangbeom Kim <sbkim73@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>