dt-bindings: pinctrl: mediatek: Add support for mt8196

dt-bindings: pinctrl: mediatek: Add support for mt8196

Add the new binding document for pinctrl on MediaTek mt8196.

Signed-off-by: Guodong Liu <guodong.liu@mediatek.com>
Signed-off-by: Cathy Xu <ot_cathy.xu@mediatek.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/20250414090215.16091-2-ot_cathy.xu@mediatek.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>