RFR: 8325108: POSIX map_memory_to_file calls release_memory unnecessarily [v2]

[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

Johan Sjölen has updated the pull request incrementally with one additional commit since the last revision:

  Check for expected invariant

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Changes:
  - all: https://git.openjdk.org/jdk/pull/29081/files
  - new: https://git.openjdk.org/jdk/pull/29081/files/f5bf7141..55ffac69

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29081&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29081&range=00-01

  Stats: 4 lines in 1 file changed: 4 ins; 0 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