netfilter: bridge: clarify bridge/netfilter message

When using bridge without bridge netfilter enabled the message
displayed is rather confusing and leads to belive that a deprecated
feature is in use. Use IS_MODULE to be explicit that the message only
affects users which use bridge netfilter as module and reword the
message.

Signed-off-by: Stefan Agner <[e-mail]>
Acked-by: Florian Westphal <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/bridge/br.c

···
 	br_fdb_test_addr_hook = br_fdb_test_addr;
 #endif
 
-	pr_info("bridge: automatic filtering via arp/ip/ip6tables has been "
-		"deprecated. Update your scripts to load br_netfilter if you "
+#if IS_MODULE(CONFIG_BRIDGE_NETFILTER)
+	pr_info("bridge: filtering via arp/ip/ip6tables is no longer available "
+		"by default. Update your scripts to load br_netfilter if you "
 		"need this.\n");
+#endif
 
 	return 0;