This fixes a problem introduced in the previous set of driver model
changes that has been seen by a lot of people (most notibly the greater
than 256 pty users, but others might also be hitting this without
realizing it.)

Also add a comment so we don't try to "fix" this again.
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>