[openssl/openssl] b175e8: Fix incomplete error check on RSA_public_decrypt()

[Niels Dossche]

  Branch: refs/heads/openssl-3.1
  Home:   https://github.com/openssl/openssl
  Commit: b175e870e97c5b9153fa3bd18375402673fdddcf
      https://github.com/openssl/openssl/commit/b175e870e97c5b9153fa3bd18375402673fdddcf
  Author: ndossche <niels.dossche at ugent.be>
  Date:   2023-02-28 (Tue, 28 Feb 2023)

  Changed paths:
    M providers/implementations/signature/rsa_sig.c

  Log Message:
  -----------
  Fix incomplete error check on RSA_public_decrypt()

According to the documentation and my analysis tool RSA_public_decrypt()
can return -1 on error, but this is not checked. Fix it by changing the
error condition.

CLA: trivial

Reviewed-by: Tomas Mraz <tomas at openssl.org>
Reviewed-by: Paul Dale <pauli at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20250)

(cherry picked from commit 8195e59986031f6f33e2569551d771904433fa04)