[PATCH] AT91RM9200 Ethernet: Remove 'at91_dev' and use netdev_priv()

Remove the global 'at91_dev' variable.
Use netdev_priv() instead of casting dev->priv directly.

Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>