dt-bindings: gpio: dwapb: allow gpio-ranges

Allow the generic gpio-ranges property so GPIOs can be mapped to their
corresponding pin. This way control of GPIO on pins that are already used
by other peripherals can be denied and basic pinconf can be done on pin
controllers that support it.

Signed-off-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>