lavapipe: set events to the unsignalled state on creation

this is otherwise uninitialized and not compliant with spec

Reviewed-by: Dave Airlie <airlied@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10625>

src/gallium/frontends/lavapipe/lvp_device.c

@@ -1886,6 +1886,7 @@ VKAPI_ATTR VkResult VKAPI_CALL lvp_CreateEvent(
 
    vk_object_base_init(&device->vk, &event->base, VK_OBJECT_TYPE_EVENT);
    *pEvent = lvp_event_to_handle(event);
+   event->event_storage = 0;
 
    return VK_SUCCESS;
 }