irq_domain fixes for v3.4-rc2

[Grant Likely <grant.likely@secretlab.ca>]

Hi Ben,

Here are the fixes I'm proposing for the irq_domain issues seen on
powermac.  I had originally only intended to remove the
irq_virq_count, but I already had the hint and slow path removal
patches written and reviewed, and removing them reduces the number of
failure paths, and simplifies the code quite a bit.

I've pushed this out to the following branch for testing:

git://git.secretlab.ca/git/linux-2.6 irqdomain/test

It has been boot tested on ARM, but not powerpc.  This series of three
patches applies on top of the existing irqdomain/merge branch on my
git server:

git://git.secretlab.ca/git/linux-2.6 irqdomain/merge

Can you test on your powermac?

Thanks,
g.