arm64: dts: imx8mm-venice-gw7901: fix port/phy validation

Since commit 65ac79e1 ("net: dsa: microchip: add the phylink
get_caps") the phy-mode must be set otherwise the switch driver will
assume "NA" mode and invalidate the port.

Fixes: 65ac79e1 ("net: dsa: microchip: add the phylink get_caps")
Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm-venice-gw7901.dts

@@ -626,24 +626,28 @@ ports {
 			lan1: port@0 {
 				reg = <0>;
 				label = "lan1";
+				phy-mode = "internal";
 				local-mac-address = [00 00 00 00 00 00];
 			};
 
 			lan2: port@1 {
 				reg = <1>;
 				label = "lan2";
+				phy-mode = "internal";
 				local-mac-address = [00 00 00 00 00 00];
 			};
 
 			lan3: port@2 {
 				reg = <2>;
 				label = "lan3";
+				phy-mode = "internal";
 				local-mac-address = [00 00 00 00 00 00];
 			};
 
 			lan4: port@3 {
 				reg = <3>;
 				label = "lan4";
+				phy-mode = "internal";
 				local-mac-address = [00 00 00 00 00 00];
 			};