net: dsa: Move port device node into port structure

Move the port device node structure into the port structure, from the
chip data. This information is needed in the next step of implementing
the new binding.

The chip data structure is used while parsing the whole old binding,
before the individual switch structures exist. With the new bindings,
this is reversed, the switches exist first, and the interconnections
between the switches is derived from the individual switch
bindings. Thus this chip data structure becomes unneeded.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
eviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>