tcp: add tcp_ooo_try_coalesce() helper

[ Upstream commit 58152ecbbcc6a0ce7fddd5bf5f6ee535834ece0c ]

In case skb in out_or_order_queue is the result of
multiple skbs coalescing, we would like to get a proper gso_segs
counter tracking, so that future tcp_drop() can report an accurate
number.

I chose to not implement this tracking for skbs in receive queue,
since they are not dropped, unless socket is disconnected.

CRs-Fixed: 2290234
Change-Id: I77743c0c1fbf293ff0bb4bba26eeeb2a1ff31ff1
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Git-commit: 66fb274f
Git-repo: https://android.googlesource.com/kernel/common/


Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>