thunderbolt: tb: fix use after free in tb_activate_pcie_devices

Add a ̣̣continue statement in order to avoid using a previously
free'd pointer tunnel in list_add.

Addresses-Coverity-ID: 1415336
Fixes: 9d3cce0b ("thunderbolt: Introduce thunderbolt bus and connection manager")
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>