Fix the calculation of the end address when flushing iotlb entries to
ram.  This bug has been a cause of esp dma errors, and it affects
HyperSPARC systems much worse than SuperSPARC systems.

Signed-off-by: Bob Breuer <breuerr@mc.net>
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Just in case it's not obvious from the patch as to how the dma was
broken:  Each dma mapping sets up iopte entries for the iommu, and the
iommu only looks in main memory for the iopte entries.  If there is a
group of iopte entries that are smaller than a page in size, but
straddle a page boundary, the broken code would fail to flush the last
page to ram.

Bob