ARM: mvebu: Add Netgear ReadyNAS 104 board

Main hardware parts of the (Armada 370 based) NETGEAR ReadyNAS 104 are
supported by mainline kernel (USB 3.0 rear ports, USB 2.0 front port,
Gigabit controller and PHYs, serial port, LEDs, buttons, SATA ports,
G762 fan controller) and referenced in provided .dts file. Some additonal
work remains for:

 - Intersil ISL12057 I2C RTC and Alarm chip: working driver but needs
   to be splitted for submission of RTC part first;
 - Front LCD (Winstar 1602G): driver needs to be written
 - Armada NAND controller (to access onboard 128MB of NAND): support
   being pushed by @free-electrons people
 - 4 front SATA LEDs controlled via GPIO brought by NXP PCA9554:
   driver is available upstream. Not referenced/tested yet.

but the device is usable w/o those.

Signed-off-by: Arnaud Ebalard <arno@natisbad.org>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>