arm: dts: imx8mm-venice-gw7901.dts: fix dsa switch configuration

Fix the dsa switch config:
- remove the unnecessary phy-mode from the switch itself
- added the necessary fixed-link node to the non-cpu ports required
  for U-Boot DSA

Signed-off-by: Tim Harvey <tharvey@gateworks.com>

arch/arm/dts/imx8mm-venice-gw7901.dts

@@ -577,7 +577,6 @@
 		pinctrl-0 = <&pinctrl_ksz>;
 		interrupt-parent = <&gpio4>;
 		interrupts = <18 IRQ_TYPE_EDGE_FALLING>;
-		phy-mode = "rgmii-id";
 
 		ports {
 			#address-cells = <1>;
@@ -587,24 +586,32 @@
 				reg = <0>;
 				label = "lan1";
 				local-mac-address = [00 00 00 00 00 00];
+				phy-handle = <&sw_phy0>;
+				phy-mode = "internal";
 			};
 
 			lan2: port@1 {
 				reg = <1>;
 				label = "lan2";
 				local-mac-address = [00 00 00 00 00 00];
+				phy-handle = <&sw_phy1>;
+				phy-mode = "internal";
 			};
 
 			lan3: port@2 {
 				reg = <2>;
 				label = "lan3";
 				local-mac-address = [00 00 00 00 00 00];
+				phy-handle = <&sw_phy2>;
+				phy-mode = "internal";
 			};
 
 			lan4: port@3 {
 				reg = <3>;
 				label = "lan4";
 				local-mac-address = [00 00 00 00 00 00];
+				phy-handle = <&sw_phy3>;
+				phy-mode = "internal";
 			};
 
 			port@5 {
@@ -619,6 +626,34 @@
 				};
 			};
 		};
+
+		mdios {
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			mdio@0 {
+				reg = <0>;
+				compatible = "microchip,ksz-mdio";
+				#address-cells = <1>;
+				#size-cells = <0>;
+
+				sw_phy0: ethernet-phy@0 {
+					reg = <0x0>;
+				};
+
+				sw_phy1: ethernet-phy@1 {
+					reg = <0x1>;
+				};
+
+				sw_phy2: ethernet-phy@2 {
+					reg = <0x2>;
+				};
+
+				sw_phy3: ethernet-phy@3 {
+					reg = <0x3>;
+				};
+			};
+		};
 	};
 
 	crypto@60 {