drm/msm: Fix imported a750 snapshot header for upstream

Add A7XX prefixes necessary because we use the same code for dumping
a6xx and a7xx, fix register name prefixes for upstream, and use the
upstream header.
Patchwork: https://patchwork.freedesktop.org/patch/592517/Signed-off-by: Connor Abbott <cwabbott0@gmail.com>
Patchwork: https://patchwork.freedesktop.org/patch/592517Signed-off-by: Rob Clark <robdclark@chromium.org>