dt-bindings: pinctrl: mt8195: Use real world values for drive-strength arguments

The original binding submission for MT8195 pinctrl described the
possible drive strength values in micro-amps in its description, but
then proceeded to list register values in its device tree binding
constraints.

However, the macros used with the Mediatek pinctrl bindings directly
specify the drive strength in micro-amps, instead of hardware register
values. The current driver implementation in Linux does convert the
value from micro-amps to hardware register values. This implementation
is also used with MT7622 and MT8183, which use real world values in
their device trees.

Given the above, it was likely an oversight to use the raw register
values in the binding. Correct the values in the binding. Also drop
the description since the binding combined with its parent,
pinctrl/pincfg.yaml, the binding is now self-describing.

Fixes: 7f766389

 ("dt-bindings: pinctrl: mt8195: add pinctrl file and binding document")
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210726111941.1447057-1-wenst@chromium.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>