Add missing cross modifying fence in nmethod entry barriers

The following test failed in the JDK21 CI:

vmTestbase/gc/vector/NonbranchyTreeHigh/TestDescription.java

Here's a snippet from the log file:

#section:main
----------messages:(6/330)----------
command: main gc.vector.SimpleGC.SimpleGC -ms high -gp nonbranchyTree(high)
reason: User specified action: run main/othervm gc.vector.SimpleGC.SimpleGC -ms high -gp nonbranchyTree(high)
started: Fri Jun 16 18:15:40 UTC 2023
Mode: othervm [/othervm specified]
finished: Fri Jun 16 18:15:51 UTC 2023
elapsed time (seconds): 10.911
----------configuration:(0/0)----------
----------System.out:(34/1800)----------
Stress time: 30 seconds
Stress iterations factor: 1
Stress threads factor: 1
Stress runs factor: 1
Max memory: 1040187392
Sleep time: 500
Iterations: 0
Number of threads: 24
Run GC thread: false
Run mem diag thread: true
Run forever: false
Memory to fill out: 624112435
Array lenght: 100
Object size: 6241124
Garbage producer: nsk.share.gc.gp.tree.NonbranchyTreeProducer
Memory Strategy: high
#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x00007f5334ae0ff0, pid=4136100, tid=4136115
#
# JRE version: Java(TM) SE Runtime Environment (21.0+28) (build 21-ea+28-LTS-2348)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (21-ea+28-LTS-2348, mixed mode, sharing, tiered, compressed class ptrs, z gc, linux-amd64)
# Problematic frame:
# V [libjvm.so+0xf9aff0] ZBarrier::mark_from_young_slow_path(zaddress)+0x50
#
# Core dump will be written. Default location: Core dumps may be processed with "/opt/core.sh %p" (or dumping to /opt/mach5/mesos/work_dir/slaves/741e9afd-8c02-45c3-b2e2-9db1450d0832-S180241/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/506ba9a0-b8ed-44d8-a614-4ea7e3c52a46/runs/cd6888e5-38ba-493f-9042-829339a13225/testoutput/test-support/jtreg_open_test_hotspot_jtreg_vmTestbase_vm_gc_container/scratch/0/core.4136100)
#
# An error report file with more information is saved as:
# /opt/mach5/mesos/work_dir/slaves/741e9afd-8c02-45c3-b2e2-9db1450d0832-S180241/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/506ba9a0-b8ed-44d8-a614-4ea7e3c52a46/runs/cd6888e5-38ba-493f-9042-829339a13225/testoutput/test-support/jtreg_open_test_hotspot_jtreg_vmTestbase_vm_gc_container/scratch/0/hs_err_pid4136100.log
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#
----------System.err:(0/0)----------
----------rerun:(37/7959)*----------

<snip>

result: Failed. Unexpected exit from test [exit code: 134]