usbmon: Drop DMA mapping for setup packet

Setup packet must be visible in virtual space. There's absolutely no
good reason to implement any kind of zero-copy transfer of 8 bytes, and
the documentation in usb.h is explicit about it. So, drop DMA remapping.

Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>