drm/amdgpu: fix memory leak when ras is not supported on specific ip block

free ras_if if ras is not supported

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>