drm/msm: wait_for_completion_timeout return is never negative

wait_for_completion_timeout returns >= 0 but never
negative  - so the error check should be against equality
to 0 not <= 0.
Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/edp/edp_ctrl.c

@@ -1032,7 +1032,7 @@ static void edp_ctrl_off_worker(struct work_struct *work)
 
 	time_left = wait_for_completion_timeout(&ctrl->idle_comp,
 						msecs_to_jiffies(500));
-	if (time_left <= 0)
+	if (!time_left)
 		DBG("%s: idle pattern timedout, %lu\n",
 				__func__, time_left);