power: regulator: Add ctrl_reg and volt_reg fields for pmic

power: regulator: Add ctrl_reg and volt_reg fields for pmic

The ctrl reg contains bit fields to enable and disable regulators,
and volt_reg has the bit fields to configure the voltage values.
The registers are frequently accessed hence make them part
of dm_regulator_uclass_platdata structure.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>