drm/i915: drop unused i915.disable_vtd_wa module parameter

This is a manual revert of

commit 7a10dfa638
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Tue Apr 1 09:33:47 2014 +0200

    drm/i915: Add debug module option for VTd validation

as no users have appeared.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1455621493-6865-2-git-send-email-jani.nikula@intel.com

drivers/gpu/drm/i915/i915_params.h

@@ -56,7 +56,6 @@ struct i915_params {
 	bool load_detect_test;
 	bool reset;
 	bool disable_display;
-	bool disable_vtd_wa;
 	bool enable_guc_submission;
 	bool verbose_state_checks;
 	bool nuclear_pageflip;