amt: fix wrong return type of amt_send_membership_update()

amt_send_membership_update() would return -1 but it's return type is bool.
So, it should be used TRUE instead of -1.

Fixes: cbc21dc ("amt: add data plane of amt interface")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Link: https://lore.kernel.org/r/20220109163702.6331-1-ap420073@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: TaeheeYoo

drivers/net/amt.c

@@ -1106,7 +1106,7 @@ static bool amt_send_membership_query(struct amt_dev *amt,
 	rt = ip_route_output_key(amt->net, &fl4);
 	if (IS_ERR(rt)) {
 		netdev_dbg(amt->dev, "no route to %pI4\n", &tunnel->ip4);
-		return -1;
+		return true;
 	}
 
 	amtmq		= skb_push(skb, sizeof(*amtmq));