MAINTAINERS: Match all of bindings/arm/npcm/ as part of NPCM architecture

All files in Documentation/devicetree/bindings/arm/npcm/ belong to the
Nuvoton NPCM architecture, even when their names might not spell it out
explicitly.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Link: https://lore.kernel.org/r/20220129115228.2257310-3-j.neuschaefer@gmx.net


Signed-off-by: Joel Stanley <joel@jms.id.au>