on on LS/FS devices directly
connected to the roothub.  The xHCI host doesn't really have a TT, and the
host will throw an error when those virtual device TT fields are set for a
device connected to the roothub.  We need this check because the xHCI
driver will shortly register two roothubs: a USB 2.0 roothub and a USB 3.0
roothub.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>