drm/i915: Discard the request queue if we fail to sleep before suspend

If we fail to clear the outstanding request queue before suspending,
mark those requests as lost.

References: https://bugs.freedesktop.org/show_bug.cgi?id=102037
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170826110935.10237-3-chris@chris-wilson.co.uk
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>

drivers/gpu/drm/i915/i915_gem.c

@@ -4590,7 +4590,8 @@ int i915_gem_suspend(struct drm_i915_private *dev_priv)
 	 * reset the GPU back to its idle, low power state.
 	 */
 	WARN_ON(dev_priv->gt.awake);
-	WARN_ON(!intel_engines_are_idle(dev_priv));
+	if (WARN_ON(!intel_engines_are_idle(dev_priv)))
+		i915_gem_set_wedged(dev_priv); /* no hope, discard everything */
 
 	/*
 	 * Neither the BIOS, ourselves or any other kernel