arm64: dts: qcom: msm8996: Define parent clocks for gcc

The CLKREF clocks in GCC are parented by RPM_SMD_LN_BB_CLK, through the
CXO2 pad. Wire this up so that this is properly enabled when need by the
various PHYs.
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Link: https://lore.kernel.org/r/20200106080546.3192125-3-bjorn.andersson@linaro.orgSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

arch/arm64/boot/dts/qcom/msm8996.dtsi

@@ -443,6 +443,9 @@ gcc: clock-controller@300000 {
 			#reset-cells = <1>;
 			#power-domain-cells = <1>;
 			reg = <0x00300000 0x90000>;
+
+			clocks = <&rpmcc RPM_SMD_LN_BB_CLK>;
+			clock-names = "cxo2";
 		};
 
 		tsens0: thermal-sensor@4a9000 {