regulator: add LM363X driver

LM363X regulator driver supports LM3631 and LM3632.
LM3631 has 5 regulators. LM3632 provides 3 regulators.
One boost output and LDOs are used for the display module.
Boost voltage is configurable but always on.
Supported operations for LDOs are enabled/disabled and voltage change.

Two LDOs of LM3632 can be controlled by external pins.
Those are configured through the DT properties.

Signed-off-by: Milo Kim <milo.kim@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>