Due to Pipe C DPINVGTT has more bits on CHV.

v2: Fix comment to say VLV/CHV (Rafael)
Reviewed-by: NRafael Barbalho <rafael.barbalho@intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>