Fixes gcc '-Wunused-but-set-variable' warning:
drivers/gpu/drm/ttm/ttm_execbuf_util.c: In function 'ttm_eu_fence_buffer_objects':
drivers/gpu/drm/ttm/ttm_execbuf_util.c:190:24: warning:
 variable 'driver' set but not used [-Wunused-but-set-variable]
It not used any more after
commit 
f2c24b83ae90 ("drm/ttm: flip the switch, and convert to dma_fence")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
 
        struct ttm_buffer_object *bo;
        struct ttm_bo_global *glob;
        struct ttm_bo_device *bdev;
-       struct ttm_bo_driver *driver;
 
        if (list_empty(list))
                return;
 
        bo = list_first_entry(list, struct ttm_validate_buffer, head)->bo;
        bdev = bo->bdev;
-       driver = bdev->driver;
        glob = bo->bdev->glob;
 
        spin_lock(&glob->lru_lock);