media: hantro: Move VP8 common code

In order to introduce support for RK3399 VP8 decoding,
move some common VP8 code. This will be reused by
the RK3399 implementation, reducing code duplication.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>