regulator: tps65086: Add regulator driver for the TPS65086 PMIC

Add support for TPS65086 PMIC regulators.

The regulators set consists of 3 Step-down Controllers, 3 Step-down
Converters, 3 LDOs, 3 Load Switches, and a Sink and Source LDO. The
output voltages are configurable and are meant to supply power to a
SoC and/or other components.

Signed-off-by: Andrew F. Davis <afd@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>