drm/msm/a6xx: Fix hangcheck for IFPC

drm/msm/a6xx: Fix hangcheck for IFPC

From the hangcheck handler, KMD checks a few registers in GX
domain to see if the GPU made any progress. But it cannot access
those registers when IFPC is enabled. Since HW based hang detection
is pretty decent, lets rely on it instead of these registers when
IFPC is enabled.

Signed-off-by: Akhil P Oommen <akhilpo@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/673378/
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>