lavapipe: drop device pointer from pipeline cache

This is unused

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38198>

src/gallium/frontends/lavapipe/lvp_pipeline_cache.c

@@ -47,7 +47,6 @@ VKAPI_ATTR VkResult VKAPI_CALL lvp_CreatePipelineCache(
    else
      cache->alloc = device->vk.alloc;
 
-   cache->device = device;
    *pPipelineCache = lvp_pipeline_cache_to_handle(cache);
 
    return VK_SUCCESS;

src/gallium/frontends/lavapipe/lvp_private.h

@@ -197,7 +197,6 @@ lvp_queue_device(const struct lvp_queue *queue)
 
 struct lvp_pipeline_cache {
    struct vk_object_base base;
-   struct lvp_device *device;
    VkAllocationCallbacks alloc;
 };