msm: kgsl: Update pagetable on context destruction for A20x

Ensure that pagetable is updated during context destruction. This
resolves stability issues during Camera launch/exit scenarios. Applies
only to A20x GPUs. This change is already done for Z180 device.

Change-Id: I955c7220aa8234009f5bca0a273093e47147279d
Signed-off-by: Rammohan Basavaraju <rammoh@codeaurora.org>