drm/i915/dsi: don't pretend we support SC GPIOs

drm/i915/dsi: don't pretend we support SC GPIOs

False ideas introduced in

commit 3dce7eeb6efd8a21e3665c0e030b68e21a5c8176
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Fri Mar 18 13:11:10 2016 +0200

    drm/i915/dsi: add support for DSI sequence block v2 gpio element

Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/5264e2f796c4bdc4128cff5a5e245da3038bf1b3.1460039033.git.jani.nikula@intel.com