pinctrl: sunxi: Add const qualifier to the pin descriptor

The pins description structure were declared as const, but the of_device_id
data magic was losing it silently.

Make sure we have it on both sides.

And now that we're using const, we can also remove the useless cast in probe.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

diff --cc drivers/pinctrl/pinctrl-sunxi.c
Simple merge

diff --cc drivers/pinctrl/pinctrl-sunxi.h
Simple merge