arm64: dts: microchip: sparx5_pcb135: add missing I2C mux unit addresses

The children of I2C mux should be named "i2c", according to DT schema
and bindings, and they should have unit address.

This fixes dtbs_check warnings like:

  sparx5_pcb135.dtb: i2c0-imux@0: Unevaluated properties are not allowed ('#address-cells', '#size-cells', 'i2c_sfp1', 'i2c_sfp2', 'i2c_sfp3', 'i2c_sfp4' were unexpected)

and dtc W=1 warnings:

  sparx5_pcb135_board.dtsi:172.23-180.4: Warning (simple_bus_reg): /axi@600000000/sfp-eth60: missing or empty reg/ranges property
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Steen Hegelund <Steen.Hegelund@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>

arch/arm64/boot/dts/microchip/sparx5_pcb135_board.dtsi

@@ -146,22 +146,22 @@ &i2c0_imux {
 	pinctrl-2 = <&i2cmux_s31>;
 	pinctrl-3 = <&i2cmux_s32>;
 	pinctrl-4 = <&i2cmux_pins_i>;
-	i2c_sfp1: i2c_sfp1 {
+	i2c_sfp1: i2c@0 {
 		reg = <0x0>;
 		#address-cells = <1>;
 		#size-cells = <0>;
 	};
-	i2c_sfp2: i2c_sfp2 {
+	i2c_sfp2: i2c@1 {
 		reg = <0x1>;
 		#address-cells = <1>;
 		#size-cells = <0>;
 	};
-	i2c_sfp3: i2c_sfp3 {
+	i2c_sfp3: i2c@2 {
 		reg = <0x2>;
 		#address-cells = <1>;
 		#size-cells = <0>;
 	};
-	i2c_sfp4: i2c_sfp4 {
+	i2c_sfp4: i2c@3 {
 		reg = <0x3>;
 		#address-cells = <1>;
 		#size-cells = <0>;