RFR: 8325108: POSIX map_memory_to_file calls release_memory unnecessarily

[Johan Sjölen]

The implementation of the function os::map_memory_to_file calls os::release_memory if a mmap:ing to a fixed location succeeds but is not at the requested location. A POSIX implementation of mmap is not allowed to succeed and return a different base address if `MAP_FIXED` is supplied, so this is dead code. We can remove it.

Quote:

>When MAP_FIXED is set in the flags argument, the implementation is informed that the value of pa shall be addr, exactly. If MAP_FIXED is set, mmap() may return MAP_FAILED and set errno to [EINVAL]. If a MAP_FIXED request is successful, the mapping established by mmap() replaces any previous mappings for the process' pages in the range [pa,pa+len).

https://pubs.opengroup.org/onlinepubs/009604499/functions/mmap.html

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Commit messages:
 - Remove dead branch

Changes: https://git.openjdk.org/jdk/pull/29081/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29081&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325108
  Stats: 6 lines in 1 file changed: 0 ins; 6 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/29081.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29081/head:pull/29081

PR: https://git.openjdk.org/jdk/pull/29081