RFR: JDK-8287194: build failure on riscv after JDK-8286825

[Feilong Jiang]

[JDK-8286825](https://bugs.openjdk.java.net/browse/JDK-8286825) made some renaming of hotspot file and method, the following naming changes are missing in riscv:
- universalNativeInvoker*--> downcallLinker*
- 'native invoker' -> 'downcall stub'

Additional testing:
-  [x] riscv release build

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Commit messages:
 - build failure on riscv after JDK-8286825

Changes: https://git.openjdk.java.net/jdk/pull/8859/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8859&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287194
  Stats: 9 lines in 1 file changed: 0 ins; 0 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8859.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8859/head:pull/8859

PR: https://git.openjdk.java.net/jdk/pull/8859