ARM: at91/dt: add Calao DAB-MMX daugther board support for USB-A9G20

ARM: at91/dt: add Calao DAB-MMX daugther board support for USB-A9G20

http://www.calao-systems.com/articles.php?lng=en&pg=6099

this daughter board add the following device:
 - Micro-SD socket
 - TTL 3V3 - (Tx/Rx/RTS/CTS)
 - I2C port
 - 0.96" Serial OLED Display Module (over UART)
 - MP3 decoder with Micro & Speakers
 - 4x PB, 4x Leds (Blue), 3x Leds (Green, Orange, Red)

for now we add only the 2 UARTs, 4 Buttons, 7 leds and i2c via DT

used_led1 will not be re-add via DT as it's used by the motherboard too

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>