mlxsw: spectrum: Enable VxLAN enslavement to VLAN-aware bridges

Commit 1c30d183 ("mlxsw: spectrum: Enable VxLAN enslavement to
bridges") enabled the enslavement of VxLAN devices to bridges that have
mlxsw ports (or their upper) as slaves. This patch extends mlxsw to also
support VLAN-aware bridges.

The patch is similar in nature to mentioned commit, but there is one
major difference. With VLAN-aware bridges, the VxLAN device's VNI is
mapped to the VLAN that is configured as PVID and egress untagged on the
bridge port.

Therefore, the driver is extended to listen to VLAN configuration on
VxLAN devices of interest and enable / disable NVE encapsulation on the
corresponding 802.1Q FIDs.

To prevent ambiguity, the driver makes sure that a given VLAN is not
configured as PVID and egress untagged on multiple VxLAN devices. This
sanitization takes place both when a port is enslaved to a bridge with
existing VxLAN devices and when a VLAN is added to / removed from a
VxLAN device of interest.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>