uas: fix sense urb handling

Stop reusing sense urbs, just allocate a fresh one each time and free it
when done.

Stop storing a sense urb pointer in the scsi request, all you can do
with it is misusing.  For example requeuing the sense urb, then f*ck it
up by picking the wrong one in case tagged requests don't finish in the
same order you've submitted them.  Also note that (not-yet supported)
task management ops don't have a scsi request in the first place.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>