RFR: 8352567: [s390x] disable JFR tests requiring JFR stubs

[Vladimir Petko]

JFR stubs are not [implemented](https://github.com/openjdk/jdk/blame/06ba6cf3a137a6cdf572a876a46d18e51c248451/src/hotspot/cpu/s390/sharedRuntime_s390.cpp#L3412). 
Add platform requirement to JFR tests that require JFR stubs to skip them on S390x.

Testing: 
- s390x:

==============================
Test summary
==============================
   TEST                                              TOTAL  PASS  FAIL ERROR  SKIP   
   jtreg:test/hotspot/jtreg/applications/ctw/modules/jdk_jfr.java
                                                         0     0     0     0     0   
   jtreg:test/hotspot/jtreg/compiler/intrinsics/TestReturnOopSetForJFRWriteCheckpoint.java
                                                         0     0     0     0     0   
   jtreg:test/jdk/jdk/jfr                              630   577     0     0    53   
==============================
TEST SUCCESS


- amd64:

==============================
Test summary
==============================
   TEST                                              TOTAL  PASS  FAIL ERROR  SKIP   
   jtreg:test/hotspot/jtreg/applications/ctw/modules/jdk_jfr.java
                                                         1     1     0     0     0   
   jtreg:test/hotspot/jtreg/compiler/intrinsics/TestReturnOopSetForJFRWriteCheckpoint.java
                                                         1     1     0     0     0   
   jtreg:test/jdk/jdk/jfr                              629   622     0     0     7   
==============================
TEST SUCCESS

-------------

Commit messages:
 - fix(lint): add missing comma
 - chore: disable JFR tests on s390x

Changes: https://git.openjdk.org/jdk/pull/28444/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28444&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8352567
  Stats: 22 lines in 20 files changed: 20 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/28444.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28444/head:pull/28444

PR: https://git.openjdk.org/jdk/pull/28444