Use common digest getter for X942 KDF
Use common digest getter for X942 KDF

Reviewed-by: Richard Levitte <5fb523282dd7956571c80524edc2dccfa0bd8234@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9770)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl