net/mlx5: E-Switch, Add state to eswitch vport representors

Currently the eswitch vport reps have a valid indicator, which is
set on register and unset on unregister. However, a rep can be loaded
or not loaded when doing unregister, current driver checks if the
vport of that rep is enabled as a flag to imply the rep is loaded.
However, for ECPF, this is not valid as the host PF will enable the
vports for its VFs instead.

Add three states: {unregistered, registered, loaded}, with the
following state changes across different operations:

	create: (none)       -> unregistered
	reg:    unregistered -> registered
	load:   registered   -> loaded
	unload: loaded       -> registered
	unreg:  registered   -> unregistered

Note that the state shall only be updated inside eswitch driver rather
than individual drivers such as ETH or IB.

Signed-off-by: Bodong Wang <bodong@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Suggested-by: Mark Bloch <markb@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>