pinctrl: sunxi: Remove old sun5i pinctrl drivers

Now that we have a common pinctrl driver for all the sun5i SoCs, we can
remove the old, separate drivers.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>