[PATCH] pata_of_platform: fix no irq handling

[Alan Cox]

> > This was discussed years ago.
> > 
> > http://lkml.org/lkml/2005/11/22/159
> > http://lkml.org/lkml/2005/11/22/227
> > 
> 
> Would this break any existing platforms?  If so, can those be fixed
> together or does it become a much bigger problem that way?

Zero means no IRQ. Any platform with bits of code left over exposing IRQ
0 is already not supported by lots of driver code including libata.

As IRQs are unsigned using -1 is asking for trouble