virtio/vsock: use 'target' in notify_poll_in callback

This callback controls setting of POLLIN, POLLRDNORM output bits of poll()
syscall, but in some cases, it is incorrectly to set it, when socket has
at least 1 bytes of available data. Use 'target' which is already exists.
Signed-off-by: NArseniy Krasnov <AVKrasnov@sberdevices.ru>
Reviewed-by: NStefano Garzarella <sgarzare@redhat.com>
Signed-off-by: NPaolo Abeni <pabeni@redhat.com>

net/vmw_vsock/virtio_transport_common.c

@@ -634,10 +634,7 @@ virtio_transport_notify_poll_in(struct vsock_sock *vsk,
 				size_t target,
 				bool *data_ready_now)
 {
-	if (vsock_stream_has_data(vsk))
-		*data_ready_now = true;
-	else
-		*data_ready_now = false;
+	*data_ready_now = vsock_stream_has_data(vsk) >= target;
 
 	return 0;
 }