drm/ttm: Always and only destroy bo->ttm_resv in ttm_bo_release_list

drm/ttm: Always and only destroy bo->ttm_resv in ttm_bo_release_list

Fixes a use-after-free due to a race condition in
ttm_bo_cleanup_refs_and_unlock, which allows one task to reserve a BO
and destroy its ttm_resv while another task is waiting for it to signal
in reservation_object_wait_timeout_rcu.

v2:
* Always initialize bo->ttm_resv in ttm_bo_init_reserved
 (Christian König)

Fixes: 0d2bd2ae045d "drm/ttm: fix memory leak while individualizing BOs"
Reviewed-by: Chunming Zhou <[email protected]> # v1
Reviewed-by: Christian König <[email protected]>
Signed-off-by: Michel Dänzer <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>