mlxsw: spectrum: Extend port_orig_get for bridge devices

The function mlxsw_sp_port_orig_get returns the vport from the physical
port if needed, based on the original device.
This patch addresses the case where the original device is a bridge.
If it is vlan unaware bridge, it returns the matching vport. If it is vlan
aware bridge, there is no matching vport, and it returns the original port.

Signed-off-by: Nogah Frankel <nogahf@mellanox.com>
Signed-off-by: Yotam Gigi <yotamg@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>