media: Rename stateful codec control macros

For historical reasons, stateful codec controls are named
as {}_MPEG_{}. While we can't at this point sanely
change all control IDs (such as V4L2_CID_MPEG_VIDEO_VP8_FRAME_HEADER),
we can least change the more meaningful macros such as classes
macros.

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