intel-iommu: fix VT-d PMR disable for TXT on S3 resume

This patch is a follow on to https://lkml.org/lkml/2011/3/21/239

, which
was merged as commit 51a63e67.

This patch adds support for S3, as pointed out by Chris Wright.

Signed-off-by: Joseph Cihula <joseph.cihula@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>