ARM: dts: BCM5301X: Update pin controller node name

This fixes:
arch/arm/boot/dts/bcm4708-asus-rt-ac56u.dtb: cru-bus@100: 'pin-controller@1c0' does not match any of the regexes: '^clock-controller@[a-f0-9]+$', '^phy@[a-f0-9]+$', '^pinctrl@[a-f0-9]+$', '^syscon@[a-f0-9]+$', '^thermal@[a-f0-9]+$'
        From schema: Documentation/devicetree/bindings/mfd/brcm,cru.yaml
arch/arm/boot/dts/bcm4708-asus-rt-ac56u.dtb: pin-controller@1c0: $nodename:0: 'pin-controller@1c0' does not match '^(pinctrl|pinmux)(@[0-9a-f]+)?$'
        From schema: Documentation/devicetree/bindings/pinctrl/brcm,ns-pinmux.yaml

Ref: e7391b02 ("dt-bindings: mfd: brcm,cru: Rename pinctrl node")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>