ARM: dts: msm: Add RTC device for 8916

Add device tree information for RTC device found on PM8916
PMIC chip. The device tree entry corresponds to the bindings
already defined for qpnp-rtc.

Change-Id: Ib33649f53e4c61a0dc9e7135e4ad090e07c7f040
Signed-off-by: Mohit Aggarwal <maggarwa@codeaurora.org>