net: Export netif_get_vlan_features().

ERROR: "netif_get_vlan_features" [drivers/net/xen-netfront.ko] undefined!

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index 8725d16..381b8e2 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1983,6 +1983,7 @@
 	else
 		return 0;
 }
+EXPORT_SYMBOL(netif_get_vlan_features);
 
 /*
  * Returns true if either: