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

Documentation/devicetree/bindings/watchdog/nuvoton,npcm-wdt.txt

@@ -5,7 +5,8 @@ The watchdog supports a pre-timeout interrupt that fires 10ms before the
 expiry.
 
 Required properties:
-- compatible      : "nuvoton,npcm750-wdt" for NPCM750 (Poleg).
+- compatible      : "nuvoton,npcm750-wdt" for NPCM750 (Poleg), or
+                    "nuvoton,wpcm450-wdt" for WPCM450 (Hermon).
 - reg             : Offset and length of the register set for the device.
 - interrupts      : Contain the timer interrupt with flags for
                     falling edge.