iommu/vt-d: Fix 64-bit accesses to 32-bit DMAR_GSTS_REG

commit fda3bec12d0979aae3f02ee645913d66fbc8a26e upstream.

This is a 32-bit register. Apparently harmless on real hardware, but
causing justified warnings in simulation.

Signed-off-by: CQ Tang <cq.tang@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --cc drivers/iommu/dmar.c
Simple merge

diff --cc drivers/iommu/intr_remapping.c
Simple merge