crypto: simplify internal state handling

Uninitialized instances are not exposed to users, so this condition should
always be true.

PR-URL: https://github.com/nodejs/node/pull/23648


Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>