dt-bindings: gpio: nomadik: add optional ngpios property

This GPIO controller can support a lesser number of GPIOs than 32.
Express that in devicetree using an optional, generic property.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Link: https://lore.kernel.org/r/20240228-mbly-gpio-v2-2-3ba757474006@bootlin.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>