Make in-kernel inode 'nlink' field be "unsigned int" instead

of something arch-dependent and usually less. 

We may want to do value limiting in generic_fillattr() if people
end up caring.

include/linux/fs.h

@@ -368,7 +368,7 @@ struct inode {
 	atomic_t		i_count;
 	dev_t			i_dev;
 	umode_t			i_mode;
-	nlink_t			i_nlink;
+	unsigned int		i_nlink;
 	uid_t			i_uid;
 	gid_t			i_gid;
 	kdev_t			i_rdev;