drm/i915: Clear flushing lists on GPU reset

Owain Ainsworth noticed that the reset code failed to clear the flushing
list leaving the driver in an inconsistent state following a hung GPU.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index e58e917..cb1ddc6 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -385,6 +385,12 @@
 	 */
 	i915_gem_retire_requests(dev);
 
+	/* Remove anything from the flushing lists. The GPU cache is likely
+	 * to be lost on reset along with the data, so simply move the
+	 * lost bo to the inactive list.
+	 */
+	i915_gem_reset_flushing_list(dev);
+
 	/*
 	 * Set the domains we want to reset (GRDOM/bits 2 and 3) as
 	 * well as the reset bit (GR/bit 0).  Setting the GR bit