dt-bindings: arm: Add initial bindings for Nuvoton platform

Modify Nuvoton NPCM and MA35 platform board bindings
  - Move 'nuvoton,npcm-gcr.yaml' from 'bindings/arm/npcm' to
    'bindings/soc/nuvoton'.
  - Rename the 'bindings/arm/npcm' directory to 'bindings/arm/nuvoton'.
  - Add bindings for ARMv8-based Nuvoton SoCs and platform boards, and
    include the initial bindings for ma35d1 series development boards.

Modify MAINTAINERS
  - Remove the line for 'bindings/arm/npcm/' under ARM/NUVOTON NPCM, as it
    has been renamed.
  - Add ARM/NUVOTON MA35 for Nuvoton MA35 series SoCs maintainer and files.

Signed-off-by: Jacky Huang <ychuang3@nuvoton.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>