media: atmel: atmel-isc: add CBC to the reg offsets struct

The CBC submodule is a part of the atmel-isc pipeline, and stands for
Contrast Brightness Control. It is used to apply gains and offsets to the
luma (Y) and chroma (U, V) components of the YUV elements.
Add cbc to the reg offsets struct. This will allow different products
to have a different reg offset for this particular module.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>