media: cedrus: Add support for VP8 decoding

VP8 in Cedrus shares same engine as H264.

Note that it seems necessary to call bitstream parsing functions,
to parse frame header, otherwise decoded image is garbage. This is
contrary to what is driver supposed to do. However, values are not
really used, so this might be acceptable. It's possible that bitstream
parsing functions set some internal VPU state, which is later necessary
for proper decoding. Biggest suspect is "VP8 probs update" trigger.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
Reviewed-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>