[media] cx23885: remove btcx-risc dependency

It's just as easy to do it in the driver. This dependency only uses a
fraction of the btcx-risc module and doing it directly in the driver
adds only a few lines. The btcx-risc module is really meant for the
bttv driver, not for other drivers.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>