ARM: dts: bcm: bcm47094: add missing #cells for mdio-bus-mux

The mdio-bus-mux has no #address-cells/#size-cells property,
which causes a few dtc warnings:

arch/arm/boot/dts/bcm47094-linksys-panamera.dts:129.4-18: Warning (reg_format): /mdio-bus-mux/mdio@200:reg: property has invalid length (4 bytes) (#address-cells == 2, #size-cells == 1)
arch/arm/boot/dts/bcm47094-linksys-panamera.dtb: Warning (pci_device_bus_num): Failed prerequisite 'reg_format'
arch/arm/boot/dts/bcm47094-linksys-panamera.dtb: Warning (i2c_bus_reg): Failed prerequisite 'reg_format'
arch/arm/boot/dts/bcm47094-linksys-panamera.dtb: Warning (spi_bus_reg): Failed prerequisite 'reg_format'
arch/arm/boot/dts/bcm47094-linksys-panamera.dts:128.22-132.5: Warning (avoid_default_addr_size): /mdio-bus-mux/mdio@200: Relying on default #address-cells value
arch/arm/boot/dts/bcm47094-linksys-panamera.dts:128.22-132.5: Warning (avoid_default_addr_size): /mdio-bus-mux/mdio@200: Relying on default #size-cells value

Add the normal cell numbers.

Link: https://lore.kernel.org/r/20190722145618.1155492-1-arnd@arndb.de
Fixes: 2bebdfcd ("ARM: dts: BCM5301X: Add support for Linksys EA9500")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Olof Johansson <olof@lixom.net>

arch/arm/boot/dts/bcm47094-linksys-panamera.dts

@@ -124,6 +124,9 @@ bluebar8 {
 	};
 
 	mdio-bus-mux {
+		#address-cells = <1>;
+		#size-cells = <0>;
+
 		/* BIT(9) = 1 => external mdio */
 		mdio_ext: mdio@200 {
 			reg = <0x200>;