ARM: dts: BCM5301X: Drop invalid #usb-cells

Such property simply doesn't exist (is not documented or used anywhere).

This fixes:
arch/arm/boot/dts/bcm4708-asus-rt-ac56u.dtb: usb@21000: Unevaluated properties are not allowed ('#usb-cells' was unexpected)
        From schema: Documentation/devicetree/bindings/usb/generic-ehci.yaml
arch/arm/boot/dts/bcm4708-asus-rt-ac56u.dtb: usb@22000: Unevaluated properties are not allowed ('#usb-cells' was unexpected)
        From schema: Documentation/devicetree/bindings/usb/generic-ohci.yaml
arch/arm/boot/dts/bcm4708-asus-rt-ac56u.dtb: usb@23000: Unevaluated properties are not allowed ('#usb-cells' was unexpected)
        From schema: Documentation/devicetree/bindings/usb/generic-xhci.yaml
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Link: https://lore.kernel.org/r/20230602133455.7441-1-zajec5@gmail.comSigned-off-by: Florian Fainelli <florian.fainelli@broadcom.com>

arch/arm/boot/dts/bcm-ns.dtsi

@@ -192,8 +192,6 @@ usb2: usb2@21000 {
 			interrupt-parent = <&gic>;
 
 			ehci: usb@21000 {
-				#usb-cells = <0>;
-
 				compatible = "generic-ehci";
 				reg = <0x00021000 0x1000>;
 				interrupts = <GIC_SPI 79 IRQ_TYPE_LEVEL_HIGH>;
@@ -214,8 +212,6 @@ ehci_port2: port@2 {
 			};
 
 			ohci: usb@22000 {
-				#usb-cells = <0>;
-
 				compatible = "generic-ohci";
 				reg = <0x00022000 0x1000>;
 				interrupts = <GIC_SPI 79 IRQ_TYPE_LEVEL_HIGH>;
@@ -245,8 +241,6 @@ usb3: usb3@23000 {
 			interrupt-parent = <&gic>;
 
 			xhci: usb@23000 {
-				#usb-cells = <0>;
-
 				compatible = "generic-xhci";
 				reg = <0x00023000 0x1000>;
 				interrupts = <GIC_SPI 80 IRQ_TYPE_LEVEL_HIGH>;