ramips: Fix initial network configuration for few boards

Argus ATP52B:      ethernet didn't work because of unconfigured switch
Sparklan WCR150GN: add switch config and make single port to be LAN
Dlink DIR-645:     seems to be a redundant case

Signed-off-by: Roman Yeryomin <roman@advem.lv>

SVN-Revision: 38960