[media] cx231xx: add support for Kworld

[mchehab@redhat.com: avoided board renumberation, removed an unused #define
 and re-used the existing mb86a20s dvb attach code]
Signed-off-by: Márcio A Alves <froooozen@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>