mlxsw: spectrum: Use per-FID struct for the VLAN-aware bridge

In a very similar way to the vFIDs, make the first 4K FIDs - used in the
VLAN-aware bridge - use the new FID struct.

Upon first use of the FID by any of the ports do the following:

1) Create the FID
2) Setup a matching flooding entry
3) Create a mapping for the FID

Unlike vFIDs, upon creation of a FID we always create a global
VID-to-FID mapping, so that ports without upper vPorts can use it
instead of creating an explicit {Port, VID} to FID mapping.

When a port leaves a FID the reverse is performed. Whenever the FID's
reference count reaches zero the FID is deleted along with the global
mapping.

The per-FID struct will later allow us to configure L3 interfaces on top
of the VLAN-aware bridge.

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