xhci: fix isoc endpoint dequeue from advancing too far on transaction error

Isoc TDs usually consist of one TRB, sometimes two. When all goes well we
receive only one success event for a TD, and move the dequeue pointer to
the next TD.

This fails if the TD consists of two TRBs and we get a transfer error
on the first TRB, we will then see two events for that TD.

Fix this by making sure the event we get is for the last TRB in that TD
before moving the dequeue pointer to the next TD. This will resolve some
of the uvc and dvb issues with the
"ERROR Transfer event TRB DMA ptr not part of current TD" error message

Cc: <stable@vger.kernel.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>