Revert "drm/amdgpu: use GMC v9 KIQ workaround only for the GFXHUB" (v2)

With GFXOFF enabled, this patch will cause PCO amdgpu_test failed,
but GFXOFF is necessary for PCO, so revert the patch.

This reverts commit b83761bb.

v2: add a comment for future reference (Alex)

Reviewed-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Jack Gui <Jack.Gui@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>