drm/msm/a6xx: Poll additional DRV status

A7XX_GEN2 generation has additional TCS slots. Poll the respective
DRV status registers before pm suspend.

Fixes: 1f8c29e8 ("drm/msm/a6xx: Add A740 support")
Signed-off-by: Akhil P Oommen <akhilpo@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/673361/


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