Also:

+static struct of_platform_driver spi_ppc4xx_of_driver = {
+       .owner = THIS_MODULE,
+       .name = DRIVER_NAME,

I'd hope the PPC folk eliminate this duplication soonish.
Those fields are obvious duplicates of the driver model
fields...

+       .match_table = spi_ppc4xx_of_match,
+       .probe = spi_ppc4xx_of_probe,
+       .remove = __exit_p(spi_ppc4xx_of_remove),
+       .driver = {
+               .name = DRIVER_NAME,
+               .owner = THIS_MODULE,
+       },
+};