[media] DocBook: Add a chapter to describe media errors

[media] DocBook: Add a chapter to describe media errors

There are several errors reported by V4L that aren't described.
They can occur on almost all ioctl's. Instead of adding them
into each ioctl, create a new chapter.

For V4L, the new chapter will automatically be listed on all
places, as there's a macro used everywhere there.

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