sock_diag: Move the SOCK_DIAG_BY_FAMILY cmd declaration

It should belong to sock_diag, not inet_diag.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/sock_diag.h b/include/linux/sock_diag.h
index ba4933b..7999778 100644
--- a/include/linux/sock_diag.h
+++ b/include/linux/sock_diag.h
@@ -1,5 +1,8 @@
 #ifndef __SOCK_DIAG_H__
 #define __SOCK_DIAG_H__
+
+#define SOCK_DIAG_BY_FAMILY 20
+
 struct sk_buff;
 struct nlmsghdr;