Revert "Revert "drm/i915/chv: Use timeout mode for RC6 on chv""

The performance regression from the CHV RC6 EI->TO change is now fixed
so re-enable TO mode for better RC6 resicency.

This reverts commit e85a5c79

.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Deepak <S&lt;deepak.s@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>