EVP_PKEY_CTX_set_dsa_ functions were only available when DSA was
enabled ('no-dsa' not configured). However, that makes it impossible
to use these functions with an engine or a provider that happens to
implement DSA. This change solves that problem by shuffling these
functions to more appropriate places.
Fixes#13529
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/13530)