arm64: dts: sc7180: Add the sleep_clk to gcc-sc7180 node

The bindings say that we're supposed to have this in the node.  Who am
I to argue with the bindings?

Fixes: 90db71e480 ("arm64: dts: sc7180: Add minimal dts/dtsi files for SC7180 soc")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20200129144432.1.Ie36f0532f67b0221c1e48e7cf6863a2738716a54@changeid
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

arch/arm64/boot/dts/qcom/sc7180.dtsi

@@ -310,8 +310,9 @@
 			compatible = "qcom,gcc-sc7180";
 			reg = <0 0x00100000 0 0x1f0000>;
 			clocks = <&rpmhcc RPMH_CXO_CLK>,
-				 <&rpmhcc RPMH_CXO_CLK_A>;
-			clock-names = "bi_tcxo", "bi_tcxo_ao";
+				 <&rpmhcc RPMH_CXO_CLK_A>,
+				 <&sleep_clk>;
+			clock-names = "bi_tcxo", "bi_tcxo_ao", "sleep_clk";
 			#clock-cells = <1>;
 			#reset-cells = <1>;
 			#power-domain-cells = <1>;