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

[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` a hotspot tier1 on qemu.

Thanks,
Xiaolin

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Commit messages:
 - Fix again: MachNode size mismatch

Changes: https://git.openjdk.java.net/jdk/pull/8356/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8356&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8285437
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 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