iommu/iommu-debug: Add support for secure domain profiling

Secure domains do different amounts of work than non-secure domains, so
we need to be able to profile them separately.  Add another debugfs
file, "secure_profiling", that does the same thing as the "profiling"
file.

Change-Id: I6968036bfdcc63449f27336771b3956a2b7754f6
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>