econet: Fix crash in aun_incoming().

econet: Fix crash in aun_incoming().

commit 4e085e76cbe558b79b54cbab772f61185879bc64 upstream.

Unconditional use of skb->dev won't work here,
try to fetch the econet device via skb_dst()->dev
instead.

Suggested by Eric Dumazet.

Reported-by: Nelson Elhage <nelhage@ksplice.com>
Tested-by: Nelson Elhage <nelhage@ksplice.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Moritz Muehlenhoff <jmm@debian.org>
[jmm: Slightly adapted for 2.6.32]
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>