drivers: net: vsc9953: Add LAG support

You can now configure LAG on VSC9953's ports using the command:
ethsw [port <port_no>] aggr {[help] | show | <lag_group_no>}

A port must belong to a single LAG. By default, a port
belongs to a LAG equal to the port's number.

For each frame, a hash will be calculated based on
Source/Destination MAC addresses, Source/Destination IP(v4/v6)
addresses, Source/Destination ports. This hash will be used to
select a single egress port from LAG. This also assures
that frames from the same flow will always have the
same egress port.

Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@freescale.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>