ARM: at91/dt: Add Support for the L+G VInCo platform

The Versatile Industrial Communication platform is a community oriented
board from Landis + Gyr. It comes with:
      - an RS-485 port
      - 2 Ethernet ports
      - a wireless M-BUS
      - a 4G modem
      - a 4MB SPI flash
      - a 4GB eMMC

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>