drm/amdgpu: Fix delete nodes that have been relesed

Fix delete nodes that it has been freed.

Fixes: 5b1270be ("drm/amdgpu: add ras_err_info to identify RAS error source")
Signed-off-by: Stanley.Yang <Stanley.Yang@amd.com>
Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>