3c59x: use netdev_alloc_skb

Fix possible bug where end of receive buffer could be overwritten.
The allocation needs to allow for the reserved space. This would only happen
if device received packet greater than Ethernet standard MTU.

Change this driver to use netdev_alloc_skb rather than setting skb->dev
directly. For the initial allocation it doesn't need to be GFP_ATOMIC.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>