ARM: dts: sun8i: Fix regulator for mmc0 for sun8i-a23-gt90h-v4

Address the FIXME comment in sun8i-a23-gt90h-v4.dts now that we've
proper regulator support.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>