[media] cec.h: merge cec-edid.h into cec.h

Drop the separate cec-edid.h header and merge it into cec.h.

There was really no need to have a separate header for this.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>