media: i2c: ov9282: Split registers into common and mode specific

Currently only one mode is supported, so all registers were
dropped in one list.
In preparation for adding more modes, split out the common registers
from those which configure the mode.

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