cryptodev: Fix issue with signature generation

That patch also enables support for SHA2 hashes, and
removes support for hashes that were never supported by
cryptodev.

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1784)