jtreg: Fix failing TestRTMSpinLoopCount on PPC64

Currently PPC64 JVM does not support integer values greater than 32767 to be passed as an option. As a result the following error is observed on PPC64 on test compiler/rtm/locking/TestRTMSpinLoopCount.java:

Command line: [/home/gromero/hg/jdk11/jdk/./build/linux-ppc64le-normal-server-release/jdk/bin/java -cp /home/gromero/hg/jdk11/jdk/JTwork/classes/0/compiler/rtm/locking/TestRTMSpinLoopCount.d:/home/gromero/hg/jdk11/jdk/test/hotspot/jtreg/compiler/rtm/locking:/home/gromero/hg/jdk11/jdk/JTwork/classes/0/test/lib:/home/gromero/hg/jdk11/jdk/test/lib:/home/gromero/hg/jdk11/jdk/JTwork/classes/0:/home/gromero/hg/jdk11/jdk/test/hotspot/jtreg:/home/gromero/jtreg/lib/javatest.jar:/home/gromero/jtreg/lib/jtreg.jar -Xcomp -server -XX:-TieredCompilation -XX:+UseRTMLocking -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -Xbootclasspath/a:. -XX:+WhiteBoxAPI --add-exports java.base/jdk.internal.misc=ALL-UNNAMED -XX:CompileCommand=compileonly,compiler.testlibrary.rtm.BusyLock::test -XX:RTMRetryCount=1000 -XX:RTMSpinLoopCount=100000 -XX:-UseRTMXendForLockBusy -XX:RTMTotalCountIncrRate=1 -XX:+PrintPreciseRTMLockingStatistics compiler.testlibrary.rtm.BusyLock true 1000 ]
int RTMSpinLoopCount=100000 is outside the allowed range [ 0 ... 32767 ]
Improperly specified VM option 'RTMSpinLoopCount=100000'
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

STDERR:
 stdout: [];
 stderr: [int RTMSpinLoopCount=100000 is outside the allowed range [ 0 ... 32767 ]
Improperly specified VM option 'RTMSpinLoopCount=100000'
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.
]
 exitValue = 1

Caused by option "-XX:RTMSpinLoopCount=100_000"