msm: kgsl: Add snapshot changes for A6XX

Add the framework for A6XX snapshot and dumping of the registers
indexed registers and MVC registers section.

Change-Id: I293e9f76bca8ebae7afa5285d4d70c889b693bc8
Signed-off-by: Shrenuj Bansal <shrenujb@codeaurora.org>
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>
Signed-off-by: Lynus Vaz <lvaz@codeaurora.org>