sfc: support configuring vf spoofchk on EF10 VFs

Corresponds to the MAC_SPOOFING_TX privilege in the hardware.
Some firmware versions on some cards don't support the feature, so check
 the TX_MAC_SECURITY capability and fail EOPNOTSUPP if trying to enable
 spoofchk on a NIC that doesn't support it.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>