[openssl/openssl] eca579: Fix cast.

[Pauli]

  Branch: refs/heads/openssl-3.0
  Home:   https://github.com/openssl/openssl
  Commit: eca5796c400df5a0b02d8c202aa05ee948285f9c
      https://github.com/openssl/openssl/commit/eca5796c400df5a0b02d8c202aa05ee948285f9c
  Author: Pauli <pauli at openssl.org>
  Date:   2023-03-06 (Mon, 06 Mar 2023)

  Changed paths:
    M crypto/evp/digest.c

  Log Message:
  -----------
  Fix cast.

Fixes #20424

Reviewed-by: Shane Lontis <shane.lontis at oracle.com>
Reviewed-by: Hugo Landau <hlandau at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20425)

(cherry picked from commit b1cd268c034268f4d37c665ee4b5148f9d8700bb)