More cleanup of MSVC errors

firmware/lib/cryptolib/rsa.c

 /* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 /* Implementation of RSA signature verification which uses a pre-processed
  * key for computation. The code extends Android's RSA verification code to
  * support multiple RSA key lengths and hash digest algorithms.
  */
 
@@ skipping 152 matching lines @@
 #ifndef NDEBUG
 /* TODO(gauravsh): Replace with a macro call for logging. */
       debug("Padding: Expecting = %02x Got = %02x\n", padding[i],
               buf[i]);
 #endif
       success = 0;
     }
   }
 
   /* Check if digest matches. */
-  for (; i < sig_len; ++i) {
+  for (; i < (int)sig_len; ++i) {
     if (buf[i] != *hash++) {
 #ifndef NDEBUG
 /* TODO(gauravsh): Replace with a macro call for logging. */
       debug("Digest: Expecting = %02x Got = %02x\n", padding[i],
               buf[i]);
 #endif
       success = 0;
     }
   }
 
   Free(buf);
 
   return success;
 }