Coverity 1521557: Error handling issues

Check the return from DSA_set0_key and generate an error on failure.
Technically a false positive since the function always returns success.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from #20409)

(cherry picked from commit dd573a2)

crypto/dsa/dsa_backend.c

@@ -173,7 +173,10 @@ DSA *ossl_dsa_key_from_pkcs8(const PKCS8_PRIV_KEY_INFO *p8inf,
         ERR_raise(ERR_LIB_DSA, DSA_R_BN_ERROR);
         goto dsaerr;
     }
-    DSA_set0_key(dsa, dsa_pubkey, dsa_privkey);
+    if (!DSA_set0_key(dsa, dsa_pubkey, dsa_privkey)) {
+        ERR_raise(ERR_LIB_DSA, ERR_R_INTERNAL_ERROR);
+        goto dsaerr;
+    }
 
     goto done;