ARM: Kirkwood: update defconfig for used i2c devices, EXT4 FS, r8169

Various kirkwood boards make use of i2c devices. Ensure the defconfig
builds them. Also, EXT4 FS is also common on NAS boxes, so include it
as well. And lastly, NSA310 has a RealTek 8169 onboard.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>