thunderbolt: Increase runtime PM reference count on DP tunnel discovery

thunderbolt: Increase runtime PM reference count on DP tunnel discovery

commit c94732bda079ee66b5c3904cbb628d0cb218ab39 upstream.

If the driver is unbound and then bound back it goes over the topology
and figure out the existing tunnels. However, if it finds DP tunnel it
should make sure the domain does not runtime suspend as otherwise it
will tear down the DP tunnel unexpectedly.

Fixes: 6ac6faee5d7d ("thunderbolt: Add runtime PM for Software CM")
Cc: stable@vger.kernel.org
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>