bhyve: specify OpenSSL 1.1 API

[emaste]

Summary

OPENSSL_API_COMPAT can be used to specify the OpenSSL API version in
use, and hide interfaces that are deprecated in that version.  This is
a NFC while we're using OpenSSL 1.1.1 but will avoid deprecation
warnings when be switch to OpenSSL 3.0.  A future change can switch to
OpenSSL 3.0 APIs.

Sponsored by:   The FreeBSD Foundation

[emaste]

My thinking here is that we can add this #define to all of the software using APIs deprecated in OpenSSL 3.0 and later (which includes, dma, decryptcore, auditdistd, etc.).

[jhb]

I think that approach is fine for now, and it lets us stage things into the tree more gracefully.