[POWERPC] Revert chrp_pci_fixup_vt8231_ata devinit to fix libata on pegasos

Commit 6d98bda79bea0e1be26c0767d0e9923ad3b72f2e changed the init order
for chrp_pci_fixup_vt8231_ata().

It can not work anymore because either the irq is not yet set to 14 or
pci_get_device() returns nothing.  At least the printk() in
chrp_pci_fixup_vt8231_ata() does not trigger anymore.
pata_via works again on Pegasos with the change below.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>