platform.cpp: support for POWER9 and POWER10 on FreeBSD (#25186)
### Description
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This commit adds support for running on POWER9 and POWER10 processors on
FreeBSD. The only major difference from Linux is that FreeBSD uses
elf_aux_info() instead of getauxval().
### Motivation and Context
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Supporting POWER9 and POWER10 on FreeBSD.