CHV uses the gen8 shadow register mechanism so we shouldn't be
checking the GT FIFO status.

This effectively removes the posting read, so add an explicit
posting read using FORCEWAKE_ACK_VLV (which is what use in
vlv_forcewake_reset()).
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>