iommu: parisc: make the IOMMUs respect the segment boundary limits

Make PARISC's two IOMMU implementations not allocate a memory area spanning
LLD's segment boundary.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Kyle McMartin <kyle@parisc-linux.org>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Grant Grundler <grundler@parisc-linux.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>