cosmetics: Add #endif comment.

Originally committed as revision 10829 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/asfcrypt.h

@@ -24,4 +24,4 @@
 
 void ff_asfcrypt_dec(const uint8_t key[20], uint8_t *data, int len);
 
-#endif
+#endif /* FFMPEG_ASFCRYPT_H */