media: atmel: atmel-isc: extract CSC submodule config into separate function

The CSC submodule is a part of the atmel-isc pipeline, and stands for
Color Space Conversion. It is used to apply a matrix transformation to
RGB pixels to convert them to the YUV components.
The CSC submodule should be initialized in the product specific driver
as it's product specific. Other products can implement it differently.

[hverkuil: made isc_sama5d2_config_csc static]

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>