regulator: Remove bq24022 regulator driver

The bq24022 driver is just a specialised form of a gpio-regulator.

As all former users of it now use the gpio-regulator directly, there
is no need to keep it around.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>