[media] vcodec:mediatek:code refine for v4l2 Encoder driver

This patch remove unused header and define from haeder files

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>