fat: don't use free_clusters for fat32

It seems that the recent Windows changed specification, and it's
undocumented.  Windows doesn't update ->free_clusters correctly.

This patch doesn't use ->free_clusters by default.  (instead, add "usefree"
for forcing to use it)

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Juergen Beisert <juergen127@kreuzholzen.de>
Cc: Andreas Schwab <schwab@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/msdos_fs.h b/include/linux/msdos_fs.h
index fa253fa..0e09c00 100644
--- a/include/linux/msdos_fs.h
+++ b/include/linux/msdos_fs.h
@@ -205,7 +205,8 @@
 		 numtail:1,       /* Does first alias have a numeric '~1' type tail? */
 		 atari:1,         /* Use Atari GEMDOS variation of MS-DOS fs */
 		 flush:1,	  /* write things quickly */
-		 nocase:1;	  /* Does this need case conversion? 0=need case conversion*/
+		 nocase:1,	  /* Does this need case conversion? 0=need case conversion*/
+		 usefree:1;	  /* Use free_clusters for FAT32 */
 };
 
 #define FAT_HASH_BITS	8