net: remove LLTX in atl2 driver

When NETIF_F_LLTX is set, the atlx driver will use a private lock.
But in recent kernels this implementation seems redundant and
can cause problems where AF_PACKET sees things twice. Since
NETIF_F_LLTX is marked as deprecated and shouldn't be used in
new driver, this patch removes NETIF_F_LLTX and adds a mmiowb
before sending packet. I have tested this driver on a Eee PC.
It works well.

Signed-off-by: Kevin Hao <kexin.hao@windriver.com>
Acked-by: Jay Cliburn <jacliburn@bellsouth.net>
Signed-off-by: David S. Miller <davem@davemloft.net>