lantiq: dts: fix interrupt provider warnings

lantiq: dts: fix interrupt provider warnings

dtc has new checks for interrupt provider which revealed that the
address-cells property is missing for all interrupt provider defined in
the lantiq dts files. Add the address-cells property to silence the
warnings.

arch/mips/boot/dts/lantiq/vr9.dtsi:48.19-54.5: Warning (interrupt_provider): /biu@1f800000/icu@80200: Missing #address-cells in interrupt provider
arch/mips/boot/dts/lantiq/vr9.dtsi:71.20-78.5: Warning (interrupt_provider): /sram@1f000000/eiu@101000: Missing #address-cells in interrupt provider

Signed-off-by: Mathias Kresin <dev@kresin.me>