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>

diff --cc include/net/sock.h
Simple merge