ARM: dts: msm: Add system_pm device bindings for sdm670

Add system_pm mailbox client to send sleep and active votes
when entering system low power modes.

Change-Id: I84cb5d64a65173163fdf7dc2ab565fc66f871206
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>
diff --git a/arch/arm64/boot/dts/qcom/sdm670.dtsi b/arch/arm64/boot/dts/qcom/sdm670.dtsi
index 9679567..b84be4e 100644
--- a/arch/arm64/boot/dts/qcom/sdm670.dtsi
+++ b/arch/arm64/boot/dts/qcom/sdm670.dtsi
@@ -1009,6 +1009,11 @@
 				<CONTROL_TCS   1>;
 	};
 
+	system_pm {
+		compatible = "qcom,system-pm";
+		mboxes = <&apps_rsc 0>;
+	};
+
 	dcc: dcc_v2@10a2000 {
 		compatible = "qcom,dcc_v2";
 		reg = <0x10a2000 0x1000>,