msm: kgsl: Add a6xx gmu suspend and resume

This adds the target specific sequence which is void of any kgsl
power control interactions for suspending and resuming a gmu
based target.

Change-Id: I43b5bc14d7f757c4cc3105f892f0c19dcefe7a6e
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>