crypto: move OpenSSL specific FIPS check to its backend

crypto: move OpenSSL specific FIPS check to its backend

Our crypto API already provides a function performing a validity check
on the specified ciphername. The OpenSSL counterpart also checks for the
cipher being FIPS-enabled.

This API is cipher_valid(). Extend it so that it can provide a reason
whenever the cipher is not valid and use it in crypto.c.

This way we move any OpenSSL specific bit to its own
backend and directly use the new cipher_valid_reason() API in the
generic code.

This patch fixes compilations with mbedTLS when some OpenSSL is also
installed. The issue was introduced with:
544330fe ("crypto: Fix OPENSSL_FIPS enabled builds")

Cc: David Sommerseth <davids@openvpn.net>
Signed-off-by: Antonio Quartulli <a@unstable.cc>
Acked-by: David Sommerseth <davids@openvpn.net>
Message-Id: <20220203193655.28791-2-a@unstable.cc>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg23714.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>