drm/msm: Add A6XX device support

Add support for the A6XX family of Adreno GPUs. The biggest addition
is the GMU (Graphics Management Unit) which takes over most of the
power management of the GPU itself but in a ironic twist of fate
needs a goodly amount of management itself. Add support for the
A6XX core code, the GMU and the HFI (hardware firmware interface)
queue that the CPU uses to communicate with the GMU.

Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>