regulator: act8865: add support for act8846

Add device id and definition of registers and regulators to support
the act8846 PMU.

Signed-off-by: Beniamino Galvani <b.galvani@gmail.com>
Tested-by: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@linaro.org>