[openssl/openssl] 18308d: SSKDF with KMAC should return SIZE_MAX when EVP_KD...

[Shane]

  Branch: refs/heads/openssl-3.0
  Home:   https://github.com/openssl/openssl
  Commit: 18308d6616c13a19094b4fae5cd0d728cae4964c
      https://github.com/openssl/openssl/commit/18308d6616c13a19094b4fae5cd0d728cae4964c
  Author: slontis <shane.lontis at oracle.com>
  Date:   2023-01-12 (Thu, 12 Jan 2023)

  Changed paths:
    M doc/man7/EVP_KDF-SS.pod
    M providers/implementations/kdfs/sskdf.c
    M test/evp_kdf_test.c

  Log Message:
  -----------
  SSKDF with KMAC should return SIZE_MAX when EVP_KDF_CTX_get_kdf_size()
is used.

Fixes #19934

The existing code was looking for the digest size, and then returned
zero.

The example code in EVP_KDF-SS.pod has been corrected to not use a
digest.

Reviewed-by: Paul Dale <pauli at openssl.org>
Reviewed-by: Tomas Mraz <tomas at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/19935)

(cherry picked from commit e8add4d379075a6daef2591edd830297d469b9f4)