dt-bindings: pinctrl: mt7986: add generic bias-pull* support

Since the bias-pull-{up,down} attribute already defines in pinctrl driver
of mediatek MT7986 SoC, this patch updates bindings to support mediatek
common bias-pull* function.

Signed-off-by: Sam Shih <sam.shih@mediatek.com>
Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20221106080114.7426-4-linux@fw-web.de


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