dt-bindings: watchdog: Allow node names named 'pmic'

Watchdog is often part of more complex devices like Power Management ICs
(PMIC), e.g. on rohm,bd96801, and the schema can be referenced by a
binding describing parent (main) node. Allow another typical name for
such PMIC devices: pmic.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>