kirkwood: switch from swconfig to dsa

kirkwood: switch from swconfig to dsa

This patch removes support for swconfig and switches to dsa driver.

swconfig and switch drivers are removed. DSA driver is enabled and
configuration is adjusted.

In kirkwood only two devices have switches: Linksys EA3500 and EA4500.

WAN MAC configuration in 02_network is required because otherwise WAN
would have the same MAC address as lan interfaces. In swconfig solution
the WAN address was assigned in u-Boot to eth1. Now, as eth1 is disabled
and wan is part of the switch, we have to set it manually.

Compile tested: EA3500, EA4500
Run tested: EA4500

Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
[minor commit title/message adjustments, remove swconfig package
for devices]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>