USB: xhci: Handle canceled URBs when HC dies.

When the host controller dies (e.g. it is removed from a PCI card slot),
the xHCI driver cannot expect commands to complete.  The buggy code this
patch fixes would mark an URB as canceled and then expect the URB to be
completed when the stop endpoint command completed.  That would never
happen if the host controller was dead, so the USB core would just hang in
the disconnect code.

If the host controller died, and the driver asks to cancel an URB, free
any structures associated with that URB and immediately give it back.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>