Provide an ndo_bpf function to efx_netdev_ops that allows setting and
querying of xdp programs on an interface.

Also check that the MTU size isn't too big when setting a program or
when the MTU is explicitly set.
Signed-off-by: NCharles McLachlan <cmclachlan@solarflare.com>
Acked-by: NJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>