media: i2c: imx412: Add bulk regulator support

Depending on the platform we may need to enable and disable three separate
regulators for the imx412.

- DOVDD
Digital I/O power

- AVDD
Analog power

- DVDD
Digital core power

The addition of these regulators shouldn't affect existing users using
fixed-on/firmware-controlled regulators.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Acked-by: Daniele Alessandrelli <daniele.alessandrelli@intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>