sparc64: add the segment boundary checking to IOMMUs while merging SG entries

Some IOMMUs allocate memory areas spanning LLD's segment boundary limit.  It
forces low level drivers to have a workaround to adjust scatter lists that the
IOMMU builds.  We are in the process of making all the IOMMUs respect the
segment boundary limits to remove such work around in LLDs.

SPARC64 IOMMUs were rewritten to use the IOMMU helper functions and the commit
89c94f2f

 made the IOMMUs not allocate memory
areas spanning the segment boundary limit.

However, SPARC64 IOMMUs allocate memory areas first then try to merge them
(while some IOMMUs walk through all the sg entries to see how they can be
merged first and allocate memory areas).  So SPARC64 IOMMUs also need the
boundary limit checking when they try to merge sg entries.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>