filesystems: add missing nlink wrappers

Replace direct i_nlink updates with the respective updater function
(inc_nlink, drop_nlink, clear_nlink, inode_dec_link_count).

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

drivers/mtd/mtdchar.c

@@ -1144,7 +1144,7 @@ static void mtdchar_notify_remove(struct mtd_info *mtd)
 
 	if (mtd_ino) {
 		/* Destroy the inode if it exists */
-		mtd_ino->i_nlink = 0;
+		clear_nlink(mtd_ino);
 		iput(mtd_ino);
 	}
 }