rockchip: board: Update Odroid Go2 to Support Additional Revisions

rockchip: board: Update Odroid Go2 to Support Additional Revisions

Update the board.c file for the Odroid Go Advance to support the
Black Edition and the Odroid Go Super. The Odroid Go Advance Black
Edition differs from the original model with the addition of 2
extra buttons and an ESP8266 WiFi module. The Odroid Go Super
adds an additional 2 buttons compared to the Black Edition, along
with a larger panel and larger battery.

This change uses the value of ADC0 to determine which of these
3 models it is, and then changes the ${fdtfile} environment variable
to match the proper devicetree name in mainline Linux.

Tested on an Odroid Go Advance (first revision) and an Odroid Go Super.
The correct ${fdtfile} variable was set for each device.

Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>