The macb driver calls schedule_delayed_work() and friends, so we need
to use a struct delayed_work along with it. The conversion was
explained by David Howells on lkml Dec 5 2006:

http://lkml.org/lkml/2006/12/5/269Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>