ARM: dts: msm: add iommu test device nodes for msmfalcon

The IOMMU test framework has been updated to add support for dummy
platform devices for testing purpose.

Change-Id: I57796a3c99a8c7463d98bc82be11a962527a45fe
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>