media: cedrus: Fix H264 decoding

During H264 API overhaul subtle bug was introduced Cedrus driver.
Progressive references have both, top and bottom reference flags set.
Cedrus reference list expects only bottom reference flag and only when
interlaced frames are decoded. However, due to a bug in Cedrus check,
exclusivity is not tested and that flag is set also for progressive
references. That causes "jumpy" background with many videos.

Fix that by checking that only bottom reference flag is set in control
and nothing else.

Tested-by: Andre Heider <a.heider@gmail.com>
Fixes: cfc8c3ed ("media: cedrus: h264: Properly configure reference field")
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: <stable@vger.kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>