net: Fix frame count check fail

bc_rxtail/rxtail should always point to newly frame.
If input more than one frame before receive,
missing assignment can result in old frame lost.

Signed-off-by: larry <larry@transtekcorp.com>

net/bluetooth/bluetooth_input.c

@@ -129,6 +129,8 @@ static int bluetooth_queue_frame(FAR struct bluetooth_conn_s *conn,
       conn->bc_rxtail->bn_flink = container;
     }
 
+  conn->bc_rxtail = container;
+
 #if CONFIG_NET_BLUETOOTH_BACKLOG > 0
   /* If incrementing the count would exceed the maximum bc_backlog value,
    * then delete the oldest frame from the head of the RX queue.