dt-bindings: watchdog: npcm: Add nuvoton,wpcm450-wdt

Add a compatible string for the WPCM450 SoC, which has the same watchdog
timer.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20210406120921.2484986-5-j.neuschaefer@gmx.net


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