RFR: 8285437: riscv: Fix MachNode size mismatch for MacroAssembler::verify_oops* [v2]

[Xiaolin Zheng]

> Trivial and same as [JDK-8283737](https://bugs.openjdk.java.net/browse/JDK-8283737): in fastdebug build, MacroAssembler::verify_oop is used in match rules encodeHeapOop and decodeHeapOop, which also requires a fixed length.
> 
> Logs are inside the JBS issue, and this issue could be reproduced by using `-XX:+VerifyOops`.
> 
> Tested using `-XX:+VerifyOops` and a hotspot tier1 on qemu.
> 
> Thanks,
> Xiaolin

Xiaolin Zheng has updated the pull request incrementally with one additional commit since the last revision:

  Add some comments

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8356/files
  - new: https://git.openjdk.java.net/jdk/pull/8356/files/f52442b6..61166a48

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8356&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8356&range=00-01

  Stats: 6 lines in 1 file changed: 6 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8356.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8356/head:pull/8356

PR: https://git.openjdk.java.net/jdk/pull/8356