mlxsw: spectrum: Configure FIDs based on bridge events

Before introducing support for L3 interfaces on top of the VLAN-aware
bridge we need to add some missing infrastructure.

Such an interface can either be the bridge device itself or a VLAN
device on top of it. In the first case the router interface (RIF) is
associated with FID 1, which is created whenever the first port netdev
joins the bridge. We currently assume the default PVID is 1 and that
it's already created, as it seems reasonable. This can be extended in
the future.

However, in the second case it's entirely possible we've yet to create a
matching FID. This can happen if the VLAN device was configured before
making any bridge port member in the VLAN.

Prevent such ordering problems by using the VLAN device's CHANGEUPPER
event to configure the FID. Make the VLAN device hold a reference to the
FID and prevent it from being destroyed even if none of the port netdevs
is using it.

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>