[NET_SCHED]: turn PSCHED_TDIFF_SAFE into inline function

Also rename to psched_tdiff_bounded.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/act_police.c b/net/sched/act_police.c
index 0a5679e..65d60a3 100644
--- a/net/sched/act_police.c
+++ b/net/sched/act_police.c
@@ -298,8 +298,8 @@
 
 		PSCHED_GET_TIME(now);
 
-		toks = PSCHED_TDIFF_SAFE(now, police->tcfp_t_c,
-					 police->tcfp_burst);
+		toks = psched_tdiff_bounded(now, police->tcfp_t_c,
+					    police->tcfp_burst);
 		if (police->tcfp_P_tab) {
 			ptoks = toks + police->tcfp_ptoks;
 			if (ptoks > (long)L2T_P(police, police->tcfp_mtu))
@@ -544,8 +544,8 @@
 		}
 
 		PSCHED_GET_TIME(now);
-		toks = PSCHED_TDIFF_SAFE(now, police->tcfp_t_c,
-					 police->tcfp_burst);
+		toks = psched_tdiff_bounded(now, police->tcfp_t_c,
+					    police->tcfp_burst);
 		if (police->tcfp_P_tab) {
 			ptoks = toks + police->tcfp_ptoks;
 			if (ptoks > (long)L2T_P(police, police->tcfp_mtu))