arm64: dts: allwinner: H5: remove redundant MMC0 card detect pin

PF6 is mostly used as the CD pin for the microSD slot on H5 based
boards. So far we were referencing this pin twice: once using the
mmc0_cd_pin phandle, and then again directly as a GPIO via the pinctrl
phandle.
This will cause problems if the pinctrl driver enables strict mode, as
the second request will fail now, leading to a driver init failure.
Remove the redundant pin reference via the mmc0_cd_pin phandle.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reported-by: Chris Obbard <obbardc@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>