staging: usbip: removed dead code from receive function

The usbip_xmit function supported sending and receiving data, however
the sending part of the function was never used/executed. Renamed the
function to usbip_recv, and removed the unused code.

Signed-off-by: Bart Westgeest <bart@elbrys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>