icmp: correct the assertion that checks limit + jitter

Fixes:	4399e055ea

sys/netinet/ip_icmp.c

@@ -1148,7 +1148,7 @@ sysctl_icmplim_and_jitter(SYSCTL_HANDLER_ARGS)
 			}
 		}
 	}
-	MPASS(V_icmplim + V_icmplim_curr_jitter > 0);
+	MPASS(V_icmplim + V_icmplim_curr_jitter >= 0);
 
 	return (error);
 }

sys/netinet6/icmp6.c

@@ -2817,7 +2817,7 @@ sysctl_icmp6lim_and_jitter(SYSCTL_HANDLER_ARGS)
 			}
 		}
 	}
-	MPASS(V_icmp6errppslim + V_icmp6lim_curr_jitter > 0);
+	MPASS(V_icmp6errppslim + V_icmp6lim_curr_jitter >= 0);
 
 	return (error);
 }