mvebu: add Kobol Helios 4 device

mvebu: add Kobol Helios 4 device

The Helios 4 is a NAS from Kobol
that is powered by an Armada 38x
MicroSOM from Solidrun, similarly
to Clearfog.

This device has:
-Armada 38x CPU
 (dual core ARMv7 1.6 Ghz)
-2 GB of ECC RAM
-Gigabit ethernet (Marvell)
-2x USB 3.0 ports
-4x Sata 3.0 ports
-i2c header (J9 |>GND|SDA|SCL|VCC)
-2x 3-pin fan headers with PWM
-micro-usb port is a TTL/UART to
 USB converter connected to TTL
-MicroSD card slot
-System, 4xSata and 1xUSB LEDs

NOT WORKING: fan control

Fan Control requires a kernel patch
that is available in the Armbian
project (the "default firmware"
of this device) and named
mvebu-gpio-remove-hardcoded
-timer-assignment
This patch isn't acceptable
by OpenWrt, it should be upstreamed.
I also have that patch in my own
local OpenWrt builds,
in case you want a more
clean and less confusing patch
for upstreaming.

To install, write the disk image
on a micro SD card with dd or
win32 disk imager, insert the
card in the slot.
Check that the dip switch battery
for boot selection is as follows
Switch 1 and 2 down/off, switches
3, 4, 5 up/on.

Signed-off-by: Alberto Bursi <bobafetthotmail@gmail.com>