gianfar: Fix crashes on RX path (Was Re: [Bugme-new] [Bug 19692] New: linux-2.6.36...

The rx_recycle queue is global per device but can be accesed by many
napi handlers at the same time, so it needs full skb_queue primitives
(with locking). Otherwise, various crashes caused by broken skbs are
possible.

This patch resolves, at least partly, bugzilla bug 19692. (Because of
some doubts that there could be still something around which is hard
to reproduce my proposal is to leave this bug opened for a month.)

Fixes commit: 0fd56bb5be6455d0d42241e65aed057244665e5e ("gianfar: Add
support for skb recycling")

Reported-by: emin ak <eminak71@gmail.com>
Tested-by: emin ak <eminak71@gmail.com>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
CC: Andy Fleming <afleming@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>