msm: kgsl: Remove idle wait in kgsl_iommu_set_pf_policy()

We don't need to wait for idle before changing the pagefault
policy on the IOMMU which is a good thing because on a busy
system we may never hit idle.

Change-Id: Ic0dedbadb8f6122e32a0a34a65c54a7bca2a523c
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>