In current mlx5e ndo_set_features implementation, setting some features
can success while others can fail. Today, we return one error code which
doesn't reflect the current features status of the netdev at the end of
the ndo callback.

Set netdev->features with features which were successfully set in order
to keep the current status in case of failure. For this purpose, define
new Macro to set/unset specific feature in netdev->features.

This patch introduces a mechanism that uses feature handlers for each
feature.
Set features will call a generic handler, which will then call a specific
handler in his turn and update netdev->features according to it's return
value. Each specific handler is responsible to perform driver specific
actions, and updating params if needed.
Signed-off-by: Gal Pressman <galp@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>