Bluetooth: Add ACL MTU, available buffers and total buffers to hci_conn_info.

This provides userspace debugging tools access to ACL flow control state.

Signed-off-by: Nick Pelly <npelly@google.com>
diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index 0c20227..4989633 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -1184,6 +1184,9 @@
 	__u8     out;
 	__u16    state;
 	__u32    link_mode;
+	__u32    mtu;
+	__u32    cnt;
+	__u32    pkts;
 };
 
 struct hci_dev_req {