regulator: act8865: Add act8600 support

This patch adds act8600 support to the act8865 driver.

VBUS and USB charger supported by this chip can be added later

Tested on MIPS Creator CI20

Signed-off-by: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
Signed-off-by: Mark Brown <broonie@kernel.org>