[media] vcodec: mediatek: Add Mediatek VP8 Video Encoder Driver

Add vp8 encoder driver for MT8173

Signed-off-by: PoChun Lin <pochun.lin@mediatek.com>
Signed-off-by: Tiffany Lin <tiffany.lin@mediatek.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>