[riscv-port-jdk17u:riscv-port] RFR: 8290137: riscv: small refactoring for add_memory_int32/64

[Fei Yang]

On Mon, 3 Apr 2023 06:05:21 GMT, Dingli Zhang <dzhang at openjdk.org> wrote:

> Please review this backport to riscv-port-jdk17u.
> Backport of [JDK-8290137](https://bugs.openjdk.org/browse/JDK-8290137). Applies cleanly.
> 
> Testing:
> - Tier1-3 passed without new failure on unmacthed (release).

Marked as reviewed by fyang (Committer).

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PR Review: https://git.openjdk.org/riscv-port-jdk17u/pull/34#pullrequestreview-1370876901