mlxsw: core: Add support for packets received from LAG port

Lower layer (pci) has information if the packet is received via LAG port.
If that is the case, it fills up rx_info accordingly. However upper
layer does not care about lag_id/port_index for received packets so
convert it to local_port before passing it up. For that conversion, lag
mapping array is introduced. Upper layer is responsible for setting up
the mapping according to what is set in HW.

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