media: vimc: Implement debayer control for mean window size

Add mean window size parameter for debayer filter as a control in
vimc-debayer.

vimc-debayer was patched to allow changing mean window parameter
of the filter without needing to reload the driver. The parameter
can now be set using a v4l2-ctl control(mean_window_size).

Co-developed-by: Laís Pessine do Carmo <laispc19@gmail.com>
Signed-off-by: Laís Pessine do Carmo <laispc19@gmail.com>
Signed-off-by: Arthur Moraes do Lago <arthurmoraeslago@gmail.com>
Acked-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>