net: tcp: Correctly deal with fully duplicated buffered out of order data

TCP is a streaming protocol, this means it can set the packet boundary
at an arbitrary location. Therefor a re-transmitted packet may have the
packet boundary at a different location from the original missing segment.

The reordering logic should be able to deal with this situation and
throw away the overlapping data. This fix clears the out of order queue
when the queued data is not relevant.

Signed-off-by: Sjors Hettinga <s.a.hettinga@gmail.com>