msm: kgsl: Remove unneeded logic checking IOMMU type

There is no reason to check if the IOMMU type is not the IOMMU
at this point because we already return 0 prior to the logic
getting here. Besides, NOMMU mode doesn't deal with pagetables so
why would you take the pagetable lock.

Change-Id: I8e68e5afe540c6e59fc3d11857e9e5355301dd0f
Signed-off-by: Shrenuj Bansal <shrenujb@codeaurora.org>