hfs: convert extents_lock in a mutex

Apple Macintosh file system: The semaphore extens_lock is used as a mutex.
Convert it to the mutex API

Signed-off-by: Matthias Kaehlcke <matthias@kaehlcke.net>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/hfs/hfs_fs.h b/fs/hfs/hfs_fs.h
index ad6528819..9955232 100644
--- a/fs/hfs/hfs_fs.h
+++ b/fs/hfs/hfs_fs.h
@@ -54,7 +54,7 @@
 	struct list_head open_dir_list;
 	struct inode *rsrc_inode;
 
-	struct semaphore extents_lock;
+	struct mutex extents_lock;
 
 	u16 alloc_blocks, clump_blocks;
 	sector_t fs_blocks;