thunderbolt: Add DP IN added last in the head of the list of DP resources

If DP IN on device router exist, position it at the beginning of the DP
resources list, so that it is used before DP IN on host router. This way
external GPU will be prioritized when pairing DP IN and DP OUT for
DisplayPort tunnel setup.

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