Explicitly return errors in ttm_tt_alloc_page_directory() and
ttm_dma_tt_alloc_page_directory() instead of relying on
further logic to detect errors.
Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>