iommu: Fix off by one in dmar_get_fault_reason()

commit fefe1ed1398b81e3fadc92d11d91162d343c8836 upstream.

fault_reason - 0x20 == ARRAY_SIZE(irq_remap_fault_reasons) is
one past the end of the array.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Joerg Roedel <joerg.roedel@amd.com>
Cc: Youquan Song <youquan.song@intel.com>
Cc: walter harms <wharms@bfs.de>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/20120513170938.GA4280@elgon.mountain
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[bwh: Backported to 3.2: s/irq_remap_fault_reasons/intr_remap_fault_reasons/]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>