* Migrate the PCI code into if_iwa_pci.c.
* .. so if_iwa.c just has the generic, non-PCI-specific bits.
* Then, flesh out the rest of the bus space stuff.

The tag setup is mostly stolen from ath(4) with the extra requirement
that buffers be 256 byte aligned.  I don't know what the full requirements
are - I'm still trying to decode what's going on from the linux driver
source.