media: atmel: atmel-isc: specialize max width and max height

Move the max width and max height constants to the product specific driver
and have them in the device struct.

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>