pinctrl: sunxi: Use macros from bindings header file for DT parsing

Since we have some bindings header for our hardcoded flags, let's use them
when we can.

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