ARM: Kirkwood: add DT description for nas2big

This patch adds the DT description for the LaCie "2Big NAS" (nas2big).
This NAS is an hardware upgrade of the 2Big Network v2.

Chipset and device list:

- CPU Marvell 88F6282 1600Mhz
- SDRAM memory, 256MB DDR3 (2x128MB x8) 533Mhz
- 1 Ethernet Gigabit port (PHY Marvell 88E1518)
- Flash memory, NAND 256MB TSOP48
- I2C EEPROM, 512 bytes (AT24 type)
- PCIe SATA controller JMicron JMB360 (eSATA)
- I2C fan controller GMT G762 (with a separate alarm GPIO)
- 1 USB2 host port
- 1 push button
- 1 power switch
- 2 SATA LEDs (bi-color, blue and red)
- 1 power LED (bi-color, blue and red)
- CPLD for LEDs and start-up management (Altera Max EMP3064)

Signed-off-by: Simon Guinot <simon.guinot@sequanux.org>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>