Create product specific callback for initializing v4l2 controls.
Call this from v4l2 controls init function.

[hverkuil: made isc_sama5d2_config_ctrls 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>