realtek: initialize port masks to match the default state

realtek: initialize port masks to match the default state

All ports are disabled by default, so configure the port isolation masks
and the pm field accordingly in the setup function. When port_enable is
called for a port, the isolation masks will be set up so that traffic
can flow between the port and the CPU.

While at it, change the code to also use the traffic_set method in
rtl83xx_setup, instead of writing to the RTL838x_PORT_ISO_CTRL(i)
registers directly.

Signed-off-by: Jan Hoffmann <jan@3e8.eu>