arm64: dts: freescale: ZII: Add missing phy-mode

The DSA framework has got more picky about always having a phy-mode
for the CPU port. The imx8mq Ethernet is being configured to RMII. Set
the switch phy-mode based on this.

Additionally, the cpu label has never actually been used in the
binding, so remove it.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mq-zii-ultra.dtsi

@@ -177,7 +177,7 @@ port@1 {
 
 				port@2 {
 					reg = <2>;
-					label = "cpu";
+					phy-mode = "rev-rmii";
 					ethernet = <&fec1>;
 
 					fixed-link {