iommu: arm-smmu: add option to distinguish testbus implementations

testbus implementation is different in some hardware add an option
qcom,testbus-version to select testbus version from device tree to
support testbus interface in such hardware.

Change-Id: I826898c16783b08b2609309774b9177009cf9110
Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>