ipv4: fix rcu lock imbalance in fib_select_default()

Commit 0c838ff1ade7 (ipv4: Consolidate all default route selection
implementations.) forgot to remove one rcu_read_unlock() from
fib_select_default().

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 146bd82..562f34c 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -1189,7 +1189,7 @@
 		fib_result_assign(res, last_resort);
 	tb->tb_default = last_idx;
 out:
-	rcu_read_unlock();
+	return;
 }
 
 #ifdef CONFIG_IP_ROUTE_MULTIPATH