media: i2c: ov9282: Add support for regulators.

The sensor takes 3 supply rails - AVDD, DVDD, and DOVDD.

Add hooks into the regulator framework for each of these
regulators.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>