ARM: dts: sun7i: Remove redundant MMC pinmux tuning

Some boards override the MMC pin muxing settings in order to enable the
pull-ups and change the drive strength to a value higher than the default.

While this was needed in the earlier days, this is now the default setting
for those pins, and therefore we don't need those board-specific settings
anymore.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>