Fixes to compiler warnings in MSVC

firmware/lib/include/stateful_util.h

 /* 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.
  */
 
 /* Helper functions/wrappers for memory allocations, manipulation and
  * comparison.
  */
 
 #ifndef VBOOT_FIRMWARE_LIB_UTILITY_H_
 #define VBOOT_FIRMWARE_LIB_UTILITY_H_
 
 #include "sysincludes.h"
 
 /* Track remaining data to be read in a buffer. */
 typedef struct MemcpyState {
-  void* remaining_buf;
+  uint8_t* remaining_buf;
   uint64_t remaining_len;  /* Remaining length of the buffer. */
   uint8_t overrun;  /* Flag set to 1 when an overrun occurs. */
 } MemcpyState;
 
 /* Skip [len] bytes only if there's enough data to skip according
  * to [state].
  * On success, return a meaningless but non-NULL pointer and updates [state].
  * On failure, return NULL, set remaining_len in state to -1.
  *
  * Useful for iterating through a binary blob to populate a struct. After the
@@ skipping 25 matching lines @@
  * a constant value.
  * On success, return a meaningless but non-NULL pointer and updates [state].
  * On failure, return NULL, set remaining_len in state to -1.
  *
  * After the first failure (buffer overrun), successive calls will always fail.
  */
 const void* StatefulMemset_r(MemcpyState* state, const uint8_t val,
                              uint64_t len);
 
 #endif  /* VBOOT_FIRMWARE_LIB_UTILITY_H_ */