drm/msm: Update GMU register xml

Update GMU register xml with additional definitions for a7x family.

Signed-off-by: Akhil P Oommen <akhilpo@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/673356/


Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>