typo fix in Documentation/filesystems/vfs.txt

struct file_system_type {

	const char *name;

	int fs_flags;

        struct dentry (*mount) (struct file_system_type *, int,

        struct dentry *(*mount) (struct file_system_type *, int,

                       const char *, void *);

        void (*kill_sb) (struct super_block *);

        struct module *owner;