boringssl: Fix Mldsa65Verify return value

Mldsa65Verify was returning kDiceResultOk (0) on success and
kDiceResultPlatformError (5) on failure, whereas BoringSSL utility
functions and callers (such as DiceVerify in boringssl_mldsa65_ops.c and
boringssl_multialg_ops.c) expect 1 on success and 0 on failure.

Align Mldsa65Verify with Mldsa87Verify to return 1 on success and 0 on
failure.

Bug: b/488378332
Test: ctest
Change-Id: Ib75bbae06c2b3cbab17810e0bddccc1f82c55177
Reviewed-on: https://pigweed-review.googlesource.com/c/open-dice/+/457165

src/boringssl_mldsa_utils.c

diff --git a/src/boringssl_mldsa_utils.c b/src/boringssl_mldsa_utils.c
index e301899..c2e0286 100644
--- a/src/boringssl_mldsa_utils.c
+++ b/src/boringssl_mldsa_utils.c
@@ -116,13 +116,13 @@
   CBS_init(&cbs_public, public_key, MLDSA65_PUBLIC_KEY_SIZE);
   struct MLDSA65_public_key parsed_pub;
   if (1 != MLDSA65_parse_public_key(&parsed_pub, &cbs_public)) {
-    return kDiceResultPlatformError;
+    return 0;
   }
   if (1 != MLDSA65_verify(&parsed_pub, signature, MLDSA65_SIGNATURE_SIZE,
                           message, message_size, NULL, 0)) {
-    return kDiceResultPlatformError;
+    return 0;
   }
-  return kDiceResultOk;
+  return 1;
 }
 
 int Mldsa87Verify(const uint8_t* message, size_t message_size,