[media] cx88: move fmt, width and height to cx8800_dev

These are global properties and do not belong in the filehandle struct.

Note: the overlay related fields were just removed: they weren't used at all.

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