[PATCH] ia64: sba_iommu update

This patch does a couple things:
      * Allows iommu page size different than PAGE_SIZE.  This was
        largely done by Bjorn.  The motivation for this is that sx1000
        hardware officially only supports use of the iommu with a 4k
        page size.  Thus the default is now 4k for sx1000 and PAGE_SIZE
        for zx1.
      * Cleanup the runtime statistics gathering such that we can turn
        it on for some info w/o impacting runtime performance.