Bluetooth: Add clarifying comment why schedule_work is used

It's not obvious why schedule_work is used instead of queue_work. Add
a comment explaining why.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 85b82f7..fd6120a 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -178,6 +178,10 @@
 	hci_dev_hold(conn->hdev);
 	hci_conn_get(conn);
 
+	/* Even though we hold a reference to the hdev, many other
+	 * things might get cleaned up meanwhile, including the hdev's
+	 * own workqueue, so we can't use that for scheduling.
+	 */
 	schedule_work(&conn->le_scan_cleanup);
 }