media: vicodec: add QP controls

Instead of hardcoding the quantization parameter (or 'DEADZONE_WIDTH'
as it was called in the codec) make this configurable through two
controls: one for I frames, one for P frames.

Also allow changing these parameters and the GOP_SIZE parameter while
streaming.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>