xhci: Remove "FIXME - check all the stream rings for pending cancellations"

Even though a Set TR deq ptr command operates on a ring, and an endpoint
can have multiple rings, we can have only one Set TR deq ptr command pending.

When an endpoint with streams halts or is stopped to unlink urbs, there
will only be at most one ring active / one td being executed (the td
stopped_td points to).

So when we reset the endpoint (for a halt), or the stop command completes, we
will queue one Set TR deq ptr command at most, cancelled urbs on other stream
rings then the one being executed will have there trbs turned to nops, and
once the hcd gets around to execute that stream ring they will be simply
skipped.

So the SET_DEQ_PENDING flag in the endpoint is sufficient protection against
starting the endpoing before all stream rings are cleaned up.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>