mediatek: dts: convert pinctrl bias to the Linux generic style

mediatek: dts: convert pinctrl bias to the Linux generic style

There are two types properties here that can control the pin bias
resistors. "mediatek,pull-{up,down}-adv" and "bias-pull-{up,down}"
actually do the same thing[1]. The first type is customized by the
Mediatek and the second type is widely used in the Linux pinctrl
framework. To avoid confusing developers, unify pinctrl bias to the
new Linux generic style.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cafe19db7751269bf6b4dd2148cbfa9fbe91d651
Signed-off-by: Shiji Yang <yangshiji66@outlook.com>
Link: https://github.com/openwrt/openwrt/pull/19741
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>