RFR: 8371643: Remove ThreadLocalAllocBuffer::_reserve_for_allocation_prefetch [v4]

[Albert Mingkun Yang]

> Trivial removing obsoleted code for unsupported arch.
> 
> Test: tier1

Albert Mingkun Yang has updated the pull request incrementally with two additional commits since the last revision:

 - review
 - patch

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/28240/files
  - new: https://git.openjdk.org/jdk/pull/28240/files/d6c34da7..6c5a07ec

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28240&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28240&range=02-03

  Stats: 31 lines in 2 files changed: 0 ins; 30 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28240.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28240/head:pull/28240

PR: https://git.openjdk.org/jdk/pull/28240