Make sure the XHCI driver obeys the isochronous scheduling threshold value
as given by the XHCI hardware parameters to avoid scheduling isochronous
transfers too early.

Sponsored by: NVIDIA Networking
Approved by: re (gjb)

(cherry picked from commit d038463bd269031fa8f13c0951b223bcae02bbca)
(cherry picked from commit 2db063c4cea9ae46493dab19d70499e06f0e1ed0)