sparc/iommu: use __sbus_iommu_map_page to implement the map_sg path
This means we handle > PAGE_SIZE offsets fine, and grow the size check
so far only performed in the map_page path. We lose the optimization
to not double flush a page if it apears in multiple consecutive SG list
entries. But at least for block I/O those don't happen anymore since
we properly merge in higher layers anyway.
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>