[riscv-port-jdk17u:riscv-port] RFR: 8291893: riscv: remove fence.i used in user space

[Feilong Jiang]

On Wed, 15 Mar 2023 00:37:21 GMT, Dingli Zhang <dzhang at openjdk.org> wrote:

> Please review this backport to riscv-port-jdk17u.
> Backport of [JDK-8291893](https://bugs.openjdk.org/browse/JDK-8291893).
> 
> The original patch cannot be directly applied because of the line number, but there are no other additional changes.
> 
> Testing:
> - Tier1 passed without new failure on unmacthed (release).

Looks good.

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Marked as reviewed by fjiang (no project role).

PR: https://git.openjdk.org/riscv-port-jdk17u/pull/13