[media] dvb-usb-v2: Don't ask user to select Cypress firmware module

The dvb-usb-v2 cypress firmware module is not optional, as drivers
won't work without it. So, instead of opening a menu for the user to
manually select, let the drivers that need it to select, hiding this
option from the Kconfig menu.

Acked-by: Antti Palosaari <crope@iki.fi>
Reviewed-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>