CVE-2025-37813 usb: xhci: Fix invalid pointer dereference in Etron workaround

In the Linux kernel, the following vulnerability has been resolved: usb: xhci: Fix invalid pointer dereference in Etron workaround This check is performed before preparetransfer and preparering, so enqueue can already point at the final link TRB of a segment. And indeed it will, some 0.4% of time...