[POWERPC] celleb: Consolidate io-workarounds code

Now, we can use generic io-workarounds mechanism and the workaround
code for spider-pci. This changes Celleb PCI code to use spider-pci
code.

Signed-off-by: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>