[POWERPC] ibmebus: Move to of_device and of_platform_driver, match eHCA and eHEA drivers

Replace struct ibmebus_dev and struct ibmebus_driver with struct of_device
and struct of_platform_driver, respectively.  Match the external ibmebus
interface and drivers using it.

Signed-off-by: Joachim Fenkes <fenkes@de.ibm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Roland Dreier <rolandd@cisco.com>
Acked-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>