net: ipv6: fix missing dst ref drop in ila lwtunnel

Add missing skb_dst_drop() to drop reference to the old dst before
adding the new dst to the skb.

Fixes: 79ff2fc31e0f ("ila: Cache a route to translated address")
Cc: Tom Herbert <[e-mail]>
Signed-off-by: Justin Iurman <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

net/ipv6/ila/ila_lwt.c

···
 		}
 	}
 
+	skb_dst_drop(skb);
 	skb_dst_set(skb, dst);
 	return dst_output(net, sk, skb);