Some Arizona devices such as the WM5102 can use DVFS on their digital core,
for these devices allow the voltage range to vary in the default setup.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Arizona class devices feature an integrated LDO which is intended to
supply the digital core for the device. Provide a driver offering
minimal control of this regulator.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>