drm/i915: Use our own workqueue to avoid wedging the system along with the GPU.

Signed-off-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 5f3a259..7537f57 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -231,6 +231,7 @@
 	spinlock_t error_lock;
 	struct drm_i915_error_state *first_error;
 	struct work_struct error_work;
+	struct workqueue_struct *wq;
 
 	/* Register state */
 	u8 saveLBB;