msm: iommu: Rearrange IOMMU version check logic

There are still some client side driver who uses this API.
Rearrange this logic since we compile only iommu-v0 or
iommu-v1 driver at a time.

Change-Id: If4aac3063695b6050e983e312c36067366bf5543
Signed-off-by: Chintan Pandya <cpandya@codeaurora.org>