net: avoid a dev refcount in ip_mc_find_dev()

We hold RTNL in ip_mc_find_dev(), no need to touch device refcount.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 3df057e..36e27c2 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -153,7 +153,7 @@
  * @addr: the source address
  * @devref: if true, take a reference on the found device
  *
- * If a caller uses devref=false, it should be protected by RCU
+ * If a caller uses devref=false, it should be protected by RCU, or RTNL
  */
 struct net_device *__ip_dev_find(struct net *net, __be32 addr, bool devref)
 {