drm/amdgpu: add return value for convert_ras_err_addr

So upper layer can return failure directly if address conversion fails.

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