Repairs the breakage introduced in gcc4 fixes.  Original had expanded
to

	((struct zatm_dev *)(dev)->dev_data) = zatm_dev;

and that's what gcc4 had complained about (cast-as-lvalue).  Proper fix is,
of course,

	dev->dev_data = zatm_dev;

What we have in 2.6.10 is

	dev = (struct atm_dev *)zatm_dev;

which doesn't cause complaints, but doesn't do anything good (leak + corruption
at the very least).
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>