staging: vchiq: Fix refcounting bug in buffer_from_host()

If we fail to queue the buffer then it can never be dequeued.  This can
lead to a forever loop in stop_streaming() when we wait for everything
to finish.

Fixes: 70ec64cc ("staging: bcm2835-camera: Ensure all buffers are returned on disable")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20200722130651.GC220681@mwandaSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/vchiq-mmal/mmal-vchiq.c

@@ -441,6 +441,8 @@ buffer_from_host(struct vchiq_mmal_instance *instance,
 	ret = vchiq_queue_kernel_message(instance->service_handle, &m,
 					 sizeof(struct mmal_msg_header) +
 					 sizeof(m.u.buffer_from_host));
+	if (ret)
+		atomic_dec(&port->buffers_with_vpu);
 
 	vchiq_release_service(instance->service_handle);