[media] cx231xx: Remove hack which puts device into bulk mode

Remove a hack which was jammed into s_input to force the device into bulk mode
at runtime (an abuse of the API).  If this sort of functionality is actually
needed (aside from the existing "transfer_mode" modprobe variable), a patch
can be submitted which makes use of a private control.

Signed-off-by: Devin Heitmueller <dheitmueller@hauppauge.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>