[openssl/openssl] 52a381: Tidy up aarch64 feature detection code in armcap.c

[Tom Cosgrove]

  Branch: refs/heads/master
  Home:   https://github.com/openssl/openssl
  Commit: 52a38144b019cfda6b0e5eaa0aca88ae11661a26
      https://github.com/openssl/openssl/commit/52a38144b019cfda6b0e5eaa0aca88ae11661a26
  Author: Tom Cosgrove <tom.cosgrove at arm.com>
  Date:   2023-03-03 (Fri, 03 Mar 2023)

  Changed paths:
    M crypto/armcap.c

  Log Message:
  -----------
  Tidy up aarch64 feature detection code in armcap.c

Make the SIGILL-based code easier to read, and don't use it on Apple Silicon.

Also fix "error: 'HWCAP(2)_*' macro redefined" warnings on FreeBSD.

Fixes #20188

Change-Id: I5618bbe9444cc40cb5705c6ccbdc331c16bab794

Reviewed-by: Tomas Mraz <tomas at openssl.org>
Reviewed-by: Paul Dale <pauli at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20305)