media: add RealVideo format RV30 and RV40

RealVideo, or also spelled as Real Video, is a suite of proprietary
video compression formats developed by RealNetworks -
the specific format changes with the version.
RealVideo codecs are identified by four-character codes.
RV30 and RV40 are RealNetworks' proprietary H.264-based codecs.

Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Ming Qian <ming.qian@nxp.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>