regulator: Add regulator driver for ATC260x PMICs

Add support for the DC-DC converters and LDO regulators found in
the ATC2603C and ATC2609A chip variants of the Actions Semi ATC260x
family of PMICs.

Co-developed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
Link: https://lore.kernel.org/r/1117b1a01b3948446cb3cc407e52de3a5d4212b0.1609258905.git.cristian.ciocaltea@gmail.com


Signed-off-by: Mark Brown <broonie@kernel.org>