forward the operation context to ttm_tt_populate as well,
and the ultimate goal is swapout enablement for reserved BOs.

v2: squash in fix for vboxvideo
Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NRoger He <Hongbo.He@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>