power: axp221: Virtual VBUS detect and enable GPIOs to replace separate logic

This converts the VBUS detection and enable logic to GPIO instead of separate
axp functions and checks that have to be used aside usual GPIO functions.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>