net: Remove switchdev_ops

Now that we have converted all possible callers to using a switchdev
notifier for attributes we do not have a need for implementing
switchdev_ops anymore, and this can be removed from all drivers the
net_device structure.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>