[NET]: note that NETIF_F_LLTX is deprecated

Am Freitag, 21. September 2007 schrieb Herbert Xu:
> Please don't use LLTX in new drivers.  We're trying to get rid
> of it since it's
>
> 1) unnecessary;
> 2) causes problems with AF_PACKET seeing things twice.

I suggest to document that LLTX is deprecated.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>