arm64: dts: qcom: pms405: add rtc node

RTC is found on PMIC PMS405 and is same as other PMIC used, so add the
rtc node with compatible as qcom,pm8941-rtc

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>