drm/i915: Use FLISDSI interface for band gap reset

v2: Rebased on latest code

Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
Signed-off-by: Yogesh Mohan Marimuthu <yogesh.mohan.marimuthu@intel.com>
Reviewed-by: Jani <Nikula&lt;jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>