xhci: Don't let the USB core disable SuperSpeed ports.

Disabling SuperSpeed ports is a Very Bad Thing (TM).  It disables
SuperSpeed terminations, which means that devices will never connect at
SuperSpeed on that port.  For USB 2.0/1.1 ports, disabling the port meant
that the USB core could always get a connect status change later.  That's
not true with USB 3.0 ports.

Do not let the USB core disable SuperSpeed ports.  We can't rely on the
device speed in the port status registers, since that isn't valid until
there's a USB device connected to the port.  Instead, we use the port
speed array that's created from the Extended Capabilities registers.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Tested-by: Don Zickus <dzickus@redhat.com>
Cc: stable@kernel.org