[crac] RFR: Fix JVMCI after #41

[Anton Kozlov]

The recently added CPU_MAX feature went out of sync with JVMCI code [1].  Since this is not a real feature, but auxilary value, a distinct name for the maximum value solves the issue. 

[1] jtreg_test_hotspot_jtreg_tier1_compiler/compiler/jvmci/JVM_GetJVMCIRuntimeTest.jtr:

jdk.vm.ci.common.JVMCIError: Missing CPU feature constants: [MAX]
        at jdk.internal.vm.ci/jdk.vm.ci.hotspot.HotSpotJVMCIBackendFactory.convertFeatures(HotSpotJVMCIBackendFactory.java:79)
        at jdk.internal.vm.ci/jdk.vm.ci.hotspot.amd64.AMD64HotSpotJVMCIBackendFactory.computeFeatures(AMD64HotSpotJVMCIBackendFactory.java:53)
        at jdk.internal.vm.ci/jdk.vm.ci.hotspot.amd64.AMD64HotSpotJVMCIBackendFactory.createTarget(AMD64HotSpotJVMCIBackendFactory.java:74)
        at jdk.internal.vm.ci/jdk.vm.ci.hotspot.amd64.AMD64HotSpotJVMCIBackendFactory.createJVMCIBackend(AMD64HotSpotJVMCIBackendFactory.java:109)
        at jdk.internal.vm.ci/jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.<init>(HotSpotJVMCIRuntime.java:549)
        at jdk.internal.vm.ci/jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.runtime(HotSpotJVMCIRuntime.java:176)
        at jdk.internal.vm.ci/jdk.vm.ci.runtime.JVMCI.initializeRuntime(Native Method)
        at jdk.internal.vm.ci/jdk.vm.ci.runtime.JVMCI.getRuntime(JVMCI.java:65)
        at compiler.jvmci.JVM_GetJVMCIRuntimeTest.run(JVM_GetJVMCIRuntimeTest.java:77)
        at compiler.jvmci.JVM_GetJVMCIRuntimeTest.main(JVM_GetJVMCIRuntimeTest.java:70)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.base/java.lang.reflect.Method.invoke(Method.java:568)
        at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:127)
        at java.base/java.lang.Thread.run(Thread.java:833)

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Commit messages:
 - Fix JVMCI after #41

Changes: https://git.openjdk.org/crac/pull/88/files
 Webrev: https://webrevs.openjdk.org/?repo=crac&pr=88&range=00
  Stats: 12 lines in 2 files changed: 2 ins; 3 del; 7 mod
  Patch: https://git.openjdk.org/crac/pull/88.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/88/head:pull/88

PR: https://git.openjdk.org/crac/pull/88