Frames that are not considered for LRO should not be counted in LRO stats.

[np]

Summary

The code will currently count any (even non-TCP) frame as queued/flushed
in the LRO stats if IFCAP_LRO is disabled or csum_flags is 0. It would
have been cleaner for tcp_lro_queue_mbuf to be able to return
TCP_LRO_CANNOT and let the caller figure out what to do. But I don't
want to touch the KPI and all the drivers so the proposed change fixes
the stats only.

[• hselasky]

Might want to ask @gallatin for a review aswell.