Update ssl3_get_channel_id for the simpler ECDSA_do_verify.

The return values are now 1/0, not 1/0/-1.

Change-Id: If65bb08a229c7944cb439ec779df461904d0ec19
Reviewed-on: https://boringssl-review.googlesource.com/1607
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/s3_srvr.c b/ssl/s3_srvr.c
index 9ec6885..b5c50b4 100644
--- a/ssl/s3_srvr.c
+++ b/ssl/s3_srvr.c
@@ -2978,17 +2978,12 @@
 
 	/* We stored the handshake hash in |tlsext_channel_id| the first time
 	 * that we were called. */
-	switch (ECDSA_do_verify(s->s3->tlsext_channel_id, SHA256_DIGEST_LENGTH, &sig, key)) {
-	case 1:
-		break;
-	case 0:
+	if (!ECDSA_do_verify(s->s3->tlsext_channel_id, SHA256_DIGEST_LENGTH, &sig, key))
+		{
 		OPENSSL_PUT_ERROR(SSL, ssl3_get_channel_id, SSL_R_CHANNEL_ID_SIGNATURE_INVALID);
 		s->s3->tlsext_channel_id_valid = 0;
 		goto err;
-	default:
-		s->s3->tlsext_channel_id_valid = 0;
-		goto err;
-	}
+		}
 
 	memcpy(s->s3->tlsext_channel_id, p, 64);
 	ret = 1;