llvmpipe: add user memory resources to the debug global list.

Otherwise things will crash on destruction.

Reviewed-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Fixes: 9a57dceeb7 ("llvmpipe: add support for user memory pointers")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16207>

src/gallium/drivers/llvmpipe/lp_texture.c

@@ -656,6 +656,11 @@ llvmpipe_resource_from_user_memory(struct pipe_screen *_screen,
    } else
       lpr->data = user_memory;
    lpr->user_ptr = true;
+#ifdef DEBUG
+   mtx_lock(&resource_list_mutex);
+   list_addtail(&lpr->list, &resource_list.list);
+   mtx_unlock(&resource_list_mutex);
+#endif
    return &lpr->base;
 fail:
    FREE(lpr);