defconfig: arm64: msm: enable IOMMU unit test in the perf defconfig

The new IOMMU unit test is useful for performance profiling of various
IOMMU-related code paths.  Since there's no overhead in enabling
them (they don't impact performance unless they are invoked explicitly),
enable them in the performance defconfig.

Change-Id: I609fa147d393c36d36169d65cc089f860249101c
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>