xhci: remove xhci_stream_id_to_ring() helper

The one case that used this function can use the
xhci_triad_to_transfer_ring() helper instead.

Avoid having several functions doing basically the same thing.

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20210129130044.206855-9-mathias.nyman@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>