virtio-rng: block max-bytes=0

with max-bytes set to 0, quota is 0 and so device does not work.
block this to avoid user confusion

Message-Id: <73a89a42d82ec8b47358f25119b87063e4a6ea57.1721818306.git.mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

hw/virtio/virtio-rng.c

@@ -184,8 +184,9 @@ static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
 
     /* Workaround: Property parsing does not enforce unsigned integers,
      * So this is a hack to reject such numbers. */
-    if (vrng->conf.max_bytes > INT64_MAX) {
-        error_setg(errp, "'max-bytes' parameter must be non-negative, "
+    if (vrng->conf.max_bytes == 0 ||
+        vrng->conf.max_bytes > INT64_MAX) {
+        error_setg(errp, "'max-bytes' parameter must be positive, "
                    "and less than 2^63");
         return;
     }