staging: vt6656: Move vnt_rx_data to usbpipe.c

vnt_rx_data is a USB function and vnt_submit_rx_urb_complete is
the only caller therefore removing dpc.c/h files and becoming
static.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Link: https://lore.kernel.org/r/d3937276-5a47-7184-e263-84d9c9cb5c7a@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>