staging: line6: drop control URB dumping code

The usbmon feature should be used instead of manually dumping control
URBs.  There are a few advantages to using usbmon:

 * Can be turned on/off at runtime
 * Provides full USB-level traffic
 * tcpdump and wireshark support for powerful analysis
 * No driver-specific code is required

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>