SELinux: Convert the netif code to use ifindex values

The current SELinux netif code requires the caller have a valid net_device
struct pointer to lookup network interface information.  However, we don't
always have a valid net_device pointer so convert the netif code to use
the ifindex values we always have as part of the sk_buff.  This patch also
removes the default message SID from the network interface record, it is
not being used and therefore is "dead code".

Signed-off-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 5df1207..be54433 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3853,7 +3853,7 @@
 	if (!skb->dev)
 		goto out;
 
-	err = sel_netif_sids(skb->dev, &if_sid, NULL);
+	err = sel_netif_sid(skb->iif, &if_sid);
 	if (err)
 		goto out;
 
@@ -4178,7 +4178,7 @@
 
 	isec = inode->i_security;
 	
-	err = sel_netif_sids(dev, &if_sid, NULL);
+	err = sel_netif_sid(dev->ifindex, &if_sid);
 	if (err)
 		goto out;