USB: add scatter-gather support to usbmon

This patch (as1301) adds support to usbmon for scatter-gather URBs.
The text interface looks at only the first scatterlist element, since
it never copies more than 32 bytes of data anyway.  The binary
interface copies as much data as possible up to the first
non-addressable buffer.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>