net: fix *_DIAG_MAX constants

net: fix *_DIAG_MAX constants

Follow the common pattern and define *_DIAG_MAX like:

        [...]
        __XXX_DIAG_MAX,
};

Because everyone is used to do:

        struct nlattr *attrs[XXX_DIAG_MAX+1];

        nla_parse([...], XXX_DIAG_MAX, [...]

Reported-by: Thomas Graf <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Cc: David Howells <[email protected]>
Signed-off-by: Andrey Vagin <[email protected]>
Signed-off-by: David S. Miller <[email protected]>