Merge branch 'dsa-multi-chip-prep'

Vivien Didelot says:

====================
net: dsa: preparatory patches for multi-chip

In order to introduce support for multi-chip configuration, we need to
do a few enhancements. This patchset makes the number of ports in a
switch dynamic (instead of capping to DSA_MAX_PORTS), stores the switch
and index of a port in the dsa_port structure, uses it in the slave
private structure, and exposes the bridge device a port belongs to.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>