drm/msm: Import a750 snapshot registers from kgsl

Import from kgsl commit 809ee24fe560.

Signed-off-by: Connor Abbott <cwabbott0@gmail.com>
Patchwork: https://patchwork.freedesktop.org/patch/592516/
Signed-off-by: Rob Clark <robdclark@chromium.org>

Author: cwabbott0