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: I978cbce49ed2b45be0209c2939b1b8423c68d5ec
CRs-fixed: 381875
Signed-off-by: Ranjhith Kalisamy <ranjhith@codeaurora.org>
Signed-off-by: Rajeev Kulkarni <krajeev@codeaurora.org>