Fix util/mkdef.pl

The deprecation checking code here didn't work the same way as in
Configure, and used $config{options} to find an --api= option that
was never there.  This is replaced with checking $config{api}, which
is the controlling variable for deprecation.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3126)