In ide_init_default_irq() patch I overlooked that ppc_ide_md.init_hwif_ports()
called from generic ide_init_hwif_ports() can set hwif->irq and it will
be overwritten by ide_init_default_irq() if CONFIG_PCI is defined.  Fix
it.

I will clean it up properly later after killing ide_init_hwif_ports() on
ARM{26}.  Doing it now is just wasted effort.