net: add sk_fullsock() helper

We have many places where we want to check if a socket is
not a timewait or request socket. Use a helper to avoid
hard coding this.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

[backported from net-next 1d0ab253872cdd3d8e7913f59c266c7fd01771d0]
[lorenzo@google.com: removed TCPF_NEW_SYN_RECV, and added a comment to add it back.]

Signed-off-by: Lorenzo Colitti <lorenzo@google.com>

Bug: 24163529
Change-Id: I196485fe3bbb6b471567e5865a688c93b6f52150
Git-commit: cdab04e3612c55f0906c84c3c05996a0507eab7d
Git-repo: https://android.googlesource.com/kernel/common/


Signed-off-by: Ashwanth Goli <ashwanth@codeaurora.org>