ARM: dts: qcom: msm8974: Use mboxes in smsm node

With the smsm bindings and driver finally supporting mboxes, switch to
that and stop using apcs as syscon.

Signed-off-by: Luca Weiss <luca@lucaweiss.eu>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20240619-smsm-mbox-dts-v1-1-268ab7eef779@lucaweiss.eu
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

Author: z3ntu

arch/arm/boot/dts/qcom/qcom-msm8974.dtsi

@@ -294,9 +294,7 @@
 		#address-cells = <1>;
 		#size-cells = <0>;
 
-		qcom,ipc-1 = <&apcs 8 13>;
-		qcom,ipc-2 = <&apcs 8 9>;
-		qcom,ipc-3 = <&apcs 8 19>;
+		mboxes = <0>, <&apcs 13>, <&apcs 9>, <&apcs 19>;
 
 		apps_smsm: apps@0 {
 			reg = <0>;