pinctrl: sunxi: Don't enforce bias disable (for now)

Commit 07fe64ba213f ("pinctrl: sunxi: Handle bias disable") actually
enforced enforced the disabling of the pull up/down resistors instead of
ignoring it like it was done before.

This was part of a wider rework to switch to the generic pinconf bindings,
and was meant to be merged together with DT patches that were switching to
it, and removing what was considered default values by both the binding and
the boards. This included no bias on a pin.

However, those DT patches were delayed to 4.11, which would be fine only
for a significant number boards having the bias setup wrong, which in turns
break the MMC on those boards (and possibly other devices too).

In order to avoid conflicts as much as possible, bring back the old
behaviour for 4.10, and we'll revert that commit once all the DT bits will
have landed.

Tested-by: Priit Laes <plaes@plaes.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>