Rework DSO API conditions and configuration option

'no-dso' is meaningless, as it doesn't get any macro defined.
Therefore, we remove all checks of OPENSSL_NO_DSO.  However, there may
be some odd platforms with no DSO scheme.  For those, we generate the
internal macro DSO_NONE aand use it.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/#8622)