hg: jdk/submit: Use u4 type for loop counter

[yasuenag at gmail.com]

Changeset: 1df748033c55
Author:    ysuenaga
Date:      2019-03-11 10:16 +0900
URL:       http://hg.openjdk.java.net/jdk/submit/rev/1df748033c55

Use u4 type for loop counter

! src/hotspot/share/jfr/periodic/sampling/jfrCallTrace.cpp