[PKT_SCHED]: Fix range in PSCHED_TDIFF_SAFE to 0..bound

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index 7352e45..fcb05a3 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -157,7 +157,8 @@
 	   case 1: \
 		   __delta += 1000000; \
 	   case 0: \
-		   __delta = abs(__delta); \
+ 		   if (__delta > bound || __delta < 0) \
+ 			__delta = bound; \
 	   } \
 	   __delta; \
 })