[media] dvb_usb_v2: remove usb_clear_halt() from stream

It works no longer as it was designed since we can change streaming
configuration during device operation.

Maybe it should be performed conditionally on cases when streaming
endpoint is changed. Anyhow, let it out now and add later if needed.

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