[NETFILTER]: fix format specifier for netfilter log targets

The prefix argument for nf_log_packet is a format specifier,
so don't pass the user defined string directly to it.

Signed-off-by: Philip Craig <philipc@snapgear.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/netfilter/ebt_log.c

@@ -168,7 +168,7 @@ static void ebt_log(const struct sk_buff *skb, unsigned int hooknr,
 
 	if (info->bitmask & EBT_LOG_NFLOG)
 		nf_log_packet(PF_BRIDGE, hooknr, skb, in, out, &li,
-		              info->prefix);
+		              "%s", info->prefix);
 	else
 		ebt_log_packet(PF_BRIDGE, hooknr, skb, in, out, &li,
 		               info->prefix);