RFR: 8351700: Remove code conditional on BarrierSetNMethod being null [v2]

[Fei Yang]

On Tue, 11 Mar 2025 20:00:59 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

>> All GCs started needing nmethod entry barriers as of loom so there's no longer any need to test for null nmethod entry barriers.
>
> Doug Simon has updated the pull request incrementally with one additional commit since the last revision:
> 
>   revived accidentally deleted code

src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp line 9903:

> 9901:     generate_arraycopy_stubs();
> 9902: 
> 9903:     BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();

Drive-by comment: `bs_nm` seems not used any more.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23996#discussion_r1990347462