regulator: rk808: add rk806 support

Add rk806 support to the existing rk808 regulator
driver.

This has been implemented using shengfei Xu's rk806
specific driver from the vendor tree as reference.

Co-developed-by: shengfei Xu <xsf@rock-chips.com>
Signed-off-by: shengfei Xu <xsf@rock-chips.com>
Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com>
Tested-by: Diederik de Haas <didi.debian@cknow.org> # Rock64, Quartz64 Model A + B
Tested-by: Vincent Legoll <vincent.legoll@gmail.com> # Pine64 QuartzPro64
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20230504173618.142075-15-sebastian.reichel@collabora.com
Signed-off-by: Mark Brown <broonie@kernel.org>