netdevsim: implement dev probe/remove skeleton with port initialization

Implement netdevsim bus probing of netdevsim devices. For every probed
device create a devlink instance. According to the user-passed value,
create a number of ports represented by devlink port instances.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>