ipv4: fix ineffective source address selection

When sending out multicast messages, the source address in inet->mc_addr is
ignored and rewritten by an autoselected one. This is caused by a typo in
commit 813b3b5db831 ("ipv4: Use caller's on-stack flowi as-is in output
route lookups").

Signed-off-by: Jiri Benc <jbenc@redhat.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/route.c

@@ -2072,7 +2072,7 @@ struct rtable *__ip_route_output_key(struct net *net, struct flowi4 *fl4)
 							      RT_SCOPE_LINK);
 			goto make_route;
 		}
-		if (fl4->saddr) {
+		if (!fl4->saddr) {
 			if (ipv4_is_multicast(fl4->daddr))
 				fl4->saddr = inet_select_addr(dev_out, 0,
 							      fl4->flowi4_scope);