{,vpx_scale}: normalize include guards

Change-Id: Ib8aafeee30d59521ee256dc1801e0db6b4b8a371
diff --git a/md5_utils.h b/md5_utils.h
index 81792c4..9935eae 100644
--- a/md5_utils.h
+++ b/md5_utils.h
@@ -20,8 +20,8 @@
  * Still in the public domain.
  */
 
-#ifndef MD5_H
-#define MD5_H
+#ifndef MD5_UTILS_H_
+#define MD5_UTILS_H_
 
 #define md5byte unsigned char
 #define UWORD32 unsigned int
@@ -38,4 +38,4 @@
 void MD5Final(unsigned char digest[16], struct MD5Context *context);
 void MD5Transform(UWORD32 buf[4], UWORD32 const in[16]);
 
-#endif /* !MD5_H */
+#endif  // MD5_UTILS_H_