iommu/arm-smmu: Tighten up global fault reporting

On systems which use a single, combined irq line for the SMMU, context
faults may result in us spuriously reporting global faults with zero
status registers.

This patch fixes up the fsr checks in both the context and global fault
interrupt handlers, so that we only report the fault if the fsr
indicates something did indeed go awry.

Change-Id: I5bba588077f84e68bcf05d8813e07f86b8f5a835
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
Git-commit: adaba320916d246af56821a1aab81a715091e7e5
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>