arm/dt: msm8974: Add devices for PMIC PM8941 RTC

Add device tree information for RTC device found on PM8941
PMIC chip. The device tree entry corresponds to the bindings
already defined for qpnp-rtc.

Change-Id: I80e2a7035664bd5e5ff1c76f779939ee658e853f
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>