thunderbolt: Disable PCIe extended encapsulation upon teardown properly

In case of PCIe tunnel teardown (including if caused by router unplug),
PCIe extended encapsulation bit should be cleared in downstream and
upstream routers accordingly.

Signed-off-by: Gil Fine <gil.fine@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>