drm/amdgpu: drop mem_global_referenced

Not used any more.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h

@@ -58,7 +58,6 @@ struct amdgpu_gtt_mgr {
 
 struct amdgpu_mman {
 	struct ttm_bo_device		bdev;
-	bool				mem_global_referenced;
 	bool				initialized;
 	void __iomem			*aper_base_kaddr;