ARM: sunxi: Remove useless allwinner,pull property

The allwinner,pull property set to NO_PULL was really considered our
default (and wasn't even changing the default value in the code).

Remove these properties to make it obvious that we do not set anything in
such a case.

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