RFR: 8296916: RISC-V: Move some small macro-assembler functions to header file

[Fei Yang]

Witnessed that there are some small macro-assembler functions located in file macroAssembler_riscv.cpp.
These are small functions which mostly contain only a single line of code. We should move them to the
corresponding header file so that they have a chance to be inlined.

Testing: Tier1 on linux-riscv64 HiFive unmatched board.

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Commit messages:
 - 8296916: RISC-V: Move some small macro-assembler functions to header file

Changes: https://git.openjdk.org/jdk/pull/11130/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11130&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296916
  Stats: 281 lines in 3 files changed: 100 ins; 140 del; 41 mod
  Patch: https://git.openjdk.org/jdk/pull/11130.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11130/head:pull/11130

PR: https://git.openjdk.org/jdk/pull/11130