board: az3166_iotdevkit: update SSD1306_REVERSE_MODE option

The SSD1306_REVERSE_MODE is now a devicetree property.

Update the board config, fix a:

warning: SSD1306_REVERSE_MODE (defined at
boards/arm/az3166_iotdevkit/Kconfig.defconfig:15) defined without a type

compliance warning.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>