switchdev: remove NETIF_F_HW_SWITCH_OFFLOAD feature flag

Roopa said remove the feature flag for this series and she'll work on
bringing it back if needed at a later date.

Signed-off-by: Scott Feldman <sfeldma@gmail.com>
Acked-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>