media: atmel: atmel-isc: add SUB422 and SUB420 to register offsets

The SUB submodules are a part of the atmel-isc pipeline, and stand for
Subsampling. They are used to subsample the original YUV 4:4:4 pixel ratio
aspect to either 4:2:2 or 4:2:0.
Add sub420 and sub422 to the reg offsets struct.
This will allow different products to have a different reg offset for these
particular modules.

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>