uboot-phytec

sunxi: axp221: Disable dcdc4 on sun8i (A23)

dcdc4 is not used on sun8i, disable it.

While at it also add comments to the other fixed voltages to document what
they are used for.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>