intel-iommu fixes

 - off by one in dmar_get_fault_reason() (maximal index in array is
   ARRAY_SIZE()-1, not ARRAY_SIZE())
 - NULL noise removal
 - __iomem annotation fix

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>