arm64: dts: k3-am6: Add mux-controller DT node required for muxing SERDES

Add mux-controller DT node as a child node of scm_conf. This is
required for muxing SERDES between USB, PCIe and ICSS2 SGMII.
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>

arch/arm64/boot/dts/ti/k3-am65-main.dtsi

@@ -233,6 +233,13 @@ scm_conf: scm_conf@100000 {
 		#address-cells = <1>;
 		#size-cells = <1>;
 		ranges = <0x0 0x0 0x00100000 0x1c000>;
+
+		serdes_mux: mux-controller {
+			compatible = "mmio-mux";
+			#mux-control-cells = <1>;
+			mux-reg-masks = <0x4080 0x3>, /* SERDES0 lane select */
+					<0x4090 0x3>; /* SERDES1 lane select */
+		};
 	};
 
 	dwc3_0: dwc3@4000000 {