ipvlan: egress mcast packets are not exceptional

Currently, if IPv6 is enabled on top of an ipvlan device in l3
mode, the following warning message:

 Dropped {multi|broad}cast of type= [86dd]

is emitted every time that a RS is generated and dmseg is soon
filled with irrelevant messages. Replace pr_warn with pr_debug,
to preserve debuggability, without scaring the sysadmin.
Signed-off-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ipvlan/ipvlan_core.c

@@ -498,8 +498,8 @@ static int ipvlan_process_outbound(struct sk_buff *skb)
 
 	/* In this mode we dont care about multicast and broadcast traffic */
 	if (is_multicast_ether_addr(ethh->h_dest)) {
-		pr_warn_ratelimited("Dropped {multi|broad}cast of type= [%x]\n",
-				    ntohs(skb->protocol));
+		pr_debug_ratelimited("Dropped {multi|broad}cast of type=[%x]\n",
+				     ntohs(skb->protocol));
 		kfree_skb(skb);
 		goto out;
 	}