[media] DocBook: Remove V4L generic error description for ioctl()

V4L ioctl function descripton also has a generic error chapter.
Remove it, as it is now obsoleted by a general, multi-API generic
error descriptions.

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