thunderbolt: Report consumed bandwidth in both directions

Whereas DisplayPort bandwidth is consumed only in one direction (from DP
IN adapter to DP OUT adapter), USB3 adds separate bandwidth for both
upstream and downstream directions.

For this reason extend the tunnel consumed bandwidth routines to support
both directions and implement this for DP.

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