drm/amdgpu: fix gtt_mgr bo's offset

Signed-off-by: Flora Cui <Flora.Cui@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c

@@ -128,6 +128,7 @@ int amdgpu_gtt_mgr_alloc(struct ttm_mem_type_manager *man,
 
 	if (!r) {
 		mem->start = node->start;
+		if (&tbo->mem == mem)
 			tbo->offset = (tbo->mem.start << PAGE_SHIFT) +
 			    tbo->bdev->man[tbo->mem.mem_type].gpu_offset;
 	}