pxa: magician/hx4700: Convert to gpio-regulator from bq24022
The bq24022 on these machines is a very simple regulator using gpios.
One provides the on/off functionality and a second one is used to
change the current between 100 and 500 mA.
This functionality can also be provided by the more generic gpio-regulator.
Therefore convert both machines which makes it possible to remove the
bq24022 driver later on.