iommu/arm-smmu: Cleanup context fault logging logic

The context fault handler uses a lot of magic numbers
that now have proper constants defined, so use those
constants.

Change-Id: Ic775bdbb4d617d4f96c935d7f18516e9d4740b9e
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>