Add switch setup to uci network defaults.

The 'lan' attribute is used to decide into which vlan to put the
port.
Currently 'disable' is never set, but the intention is to use this
for devices like the 8devices Carambola, which only has two ports
hooked up to the SoC.

Signed-off-by: Tobias Diedrich <ranma+openwrt@tdiedrich.de>

SVN-Revision: 33300