iommu/arm-smmu: Add support for slave side protection

For targets where we have no hypervisor, slave side protection mechanism
is used to provide buffer protection. Add functionality to make calls
into TZ for mapping/unmapping of buffers.

Change-Id: I394f56a4a35b6ce4a27ff2be5095b15f09a562c2
Signed-off-by: Chinkit Kumar,Kirti Kumar Parmar <parma@codeaurora.org>