arm64: dts: qcom: msm8916: Add clock properties to the APCS node

There are clock controller registers in the APCS block, which purpose
is to control the main CPU mux and divider. Add the clock properties as
part of the APCS device-tree node.
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>

arch/arm64/boot/dts/qcom/msm8916.dtsi

@@ -336,6 +336,8 @@ apcs: mailbox@b011000 {
 			compatible = "qcom,msm8916-apcs-kpss-global", "syscon";
 			reg = <0xb011000 0x1000>;
 			#mbox-cells = <1>;
+			clocks = <&a53pll>;
+			#clock-cells = <0>;
 		};
 
 		blsp1_uart2: serial@78b0000 {