media: atmel: atmel-isc: create callback for RLP submodule product specific

The RLP submodule is a part of the atmel-isc pipeline, and stands for
Rounding,Limiting and Packaging. It used to extract specific data from the
ISC pipeline. For example if we want to output greyscale 8 bit, we would
use limiting to 8 bits, and packaging to Luma component only.

Create a product specific callback for initializing the RLP submodule
of the pipeline

[hverkuil: made isc_sama5d2_config_rlp 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>