mlxsw: spectrum: Delete RIF when VLAN device is removed

In commit 602b74ed ("mlxsw: spectrum_switchdev: Do not leak RIFs
when removing bridge") I handled the case where RIFs created for VLAN
devices were not properly cleaned up when their real device (a bridge)
was removed.

However, I forgot to handle the case of the VLAN device itself being
removed. Do so now when the VLAN device is being unlinked from its real
device.

Fixes: 99f44bb3

 ("mlxsw: spectrum: Enable L3 interfaces on top of bridge devices")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Reported-by: Artem Shvorin <art@qrator.net>
Tested-by: Artem Shvorin <art@qrator.net>
Signed-off-by: David S. Miller <davem@davemloft.net>