Fix detection of ARMv7 and ARM64 CPU features on FreeBSD

Fix detection of ARMv7 and ARM64 CPU features on FreeBSD

OpenSSL assumes AT_HWCAP = 16 (as on Linux), but on FreeBSD AT_HWCAP = 25
Switch to using AT_HWCAP, and setting it to 16 if it is not defined.

OpenSSL calls elf_auxv_info() with AT_CANARY which returns ENOENT
resulting in all ARM acceleration features being disabled.

CLA: trivial

Reviewed-by: Ben Kaduk <kaduk@mit.edu>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17082)

(cherry picked from commit c1dabe26e3e96cdce0ffc929e9677840ad089ba5)