media: Add AV1 uAPI

This patch adds the  AOMedia Video 1 (AV1) kernel uAPI.

This design is based on currently available AV1 API implementations and
aims to support the development of AV1 stateless video codecs
on Linux.

Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Co-developed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>