arm64: dts: mediatek: mt8173: Fix pinctrl node names and cleanup

arm64: dts: mediatek: mt8173: Fix pinctrl node names and cleanup

Fix the pinctrl node names to adhere to the bindings, as the main
pin node is supposed to be named like "uart0-pins" and the pinmux
node named like "pins-bus".

While at it, also cleanup all of the MTK_DRIVE_(x)mA by changing
that to just the (x) number.

Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>