iommu/arm-smmu: ignore target specific initialization

Ignore the target specific initialization that is not required for the
slave side secure targets.

Change-Id: I172ddaf196cf216bb72f00e26183f725023b5244
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
Signed-off-by: Vishwanath Raju K <vishk@codeaurora.org>