sparc/iommu: pass a physical address to iommu_get_one

No need for the page structure, just the paddr / pfn.  This is
going to simplify fixes to the callers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>