[media] DocBook: Use the generic error code page also for MC API

Instead of having their own generic error codes at the MC API, move
its section to the generic one and be sure that all media ioctl's
will point to it.

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