drm/i915/vlv: don't save panel power sequencer registers on suspend

Don't save the panel power sequencer register on vlv/chv for two simple
reasons. First, these are the wrong registers to save to begin
with. Second, they are not restored anyway.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>