dt-bindings: mfd: Add compatible for pmk8350 rtc

Add compatible string for pmk8350 rtc support.
Signed-off-by: satya priya <skakit@codeaurora.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/mfd/qcom-pm8xxx.txt

@@ -64,6 +64,7 @@ The below bindings specify the set of valid subnodes.
 		    "qcom,pm8921-rtc"
 		    "qcom,pm8941-rtc"
 		    "qcom,pm8018-rtc"
+		    "qcom,pmk8350-rtc"
 
 - reg:
 	Usage: required