ARM: dts: sun5i: Remove card detect pull-up

Boards usually have an external pull-up on the card-detect signal, so
there's no need to add another one.

This also removes a DTC warning.

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