fib_trie: remove duplicated rcu lock

fib_table_lookup has included the rcu lock protection.
Signed-off-by: baker.zhang <baker.kernel@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/fib_frontend.c

@@ -933,7 +933,6 @@ static void nl_fib_lookup(struct fib_result_nl *frn, struct fib_table *tb)
 		local_bh_disable();
 
 		frn->tb_id = tb->tb_id;
-		rcu_read_lock();
 		frn->err = fib_table_lookup(tb, &fl4, &res, FIB_LOOKUP_NOREF);
 
 		if (!frn->err) {
@@ -942,7 +941,6 @@ static void nl_fib_lookup(struct fib_result_nl *frn, struct fib_table *tb)
 			frn->type = res.type;
 			frn->scope = res.scope;
 		}
-		rcu_read_unlock();
 		local_bh_enable();
 	}
 }