tcp: introduce tcp_data_queue_ofo

tcp: introduce tcp_data_queue_ofo

Split tcp_data_queue() in two parts for better readability.

tcp_data_queue_ofo() is responsible for queueing incoming skb into out
of order queue.

Change code layout so that the skb_set_owner_r() is performed only if
skb is not dropped.

This is a preliminary patch before "reduce out_of_order memory use"
following patch.

Signed-off-by: Eric Dumazet <[email protected]>
Cc: Neal Cardwell <[email protected]>
Cc: Yuchung Cheng <[email protected]>
Cc: H.K. Jerry Chu <[email protected]>
Cc: Tom Herbert <[email protected]>
Cc: Ilpo Järvinen <[email protected]>
Acked-by: Neal Cardwell <[email protected]>
Signed-off-by: David S. Miller <[email protected]>