xhci: handle stop endpoint command completion with endpoint in running state.

Handle race where a stop endpoint command fails with "context state error"
as hardware hasn't actually started the ring yet after a previous urb
cancellation completed and restarted the endpoint.
Flushing the doorbell write that restart the endpoint reduced these cases,
but didn't completely resolve them.

Check if the ring is running in the stop endpoint completion handler, and
issue a new stop endpoint command in this case.

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20210129130044.206855-24-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>