[parisc-linux] SuckyIO support

[Alan Cox]

> In our case, it's the IRQ region plus IRQ offset right now.
> I've proposed another IRQ scheme which would replace the math with
> a lookup table. But we haven't done anything with it yet since
> the region+offset is "good enough" for now.

Providing dev->irq is a suitable size putting a pointer into it is also 
perfectly acceptable although it makes the error reports look odd. Which
reminds me that someday we need canonicalise_irq(irq) for reporting stuff
nicely cross arch