ARM: Kirkwood: DT board setup for LaPlug

This patch adds DT board setup for the LaCie NAS LaPlug.

Chipset list:
- CPU MARVELL 88FR131 800Mhz
- SDRAM memory: 128MB DDR2-800 400Mhz
- 1 Ethernet Gigabit port (PHY MARVELL 88E1318) (To be verified)
- 1 PCI-Express port
- SPI flash, NOR 512KB
- 1 NAND 512 MB
- 1 push button
- 2 LEDs (red and blue)
- 4 USB Ports

Signed-off-by: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>