xhci: cleanup isoc tranfers queuing code

Clean up xhci_queue_isoc_tx() and helpers to prepare them for USB 3.1 and
xhci 1.1 isoc TRB changes.

Only functional change is adding xhci version 1.1 to the BEI flag check
toghether with xhci version 1.0. Both versions behave the same.

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