dt-bindings: pinctrl: mt8186: Add gpio-line-names property

Add the 'gpio-line-names' property to mt8186-pinctrl, as this will be
used in devicetrees to describe pin names.

Signed-off-by: Allen-KH Cheng <allen-kh.cheng@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220725110702.11362-2-allen-kh.cheng@mediatek.com


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