dt-bindings: pinctrl: mediatek,mt6779-pinctrl: Make gpio-ranges optional

dt-bindings: pinctrl: mediatek,mt6779-pinctrl: Make gpio-ranges optional

The pin controller can function without specifying gpio-ranges so remove
it from required properties. This is also done in preparation for adding
other pin controllers which currently don't have the gpio-ranges property
defined where they are used in DTS. This allows dtbs_check to pass on
those device trees.

Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20221028153505.23741-4-y.oudjana@protonmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>