xhci: only update dequeue ptr on completed transfers

The dequeue pointer should only be updated in case the transfer
is actually completed.  If we update it for inflight transfers
we will not pick them up again after migration, which easily
triggers with HID devices as they typically have a pending
transfer, waiting for user input to happen.

Fixes: 243afe858b95765b98d16a1f0dd50dca262858ad
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1451631
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Tested-by: Laurent Vivier <lvivier@redhat.com>
Message-id: 20170608074122.32099-1-kraxel@redhat.com
