msm: kgsl: Vote for the TBU clock while doing TLB invalidate

If the TBU clock is off while doing TLB invalidate, TLBSYNC status
is not correctly reflected, causing the system to go
into a bad state. Add it to the IOMMU clock list and vote for it.

CRs-Fixed: 832097
Change-Id: I6af0831140d50910828a5d5947ae920038889451
Signed-off-by: Anshuman Dani <adani@codeaurora.org>