ARM: dts: stm32: Add IoT Box board support

ARM: dts: stm32: Add IoT Box board support

IoT Box is an IoT gateway device based on Stinger96 board powered by
STM32MP1 SoC, designed and manufactured by Shiratech Solutions. This
device makes use of Stinger96 board by having it as a base board with
one additional mezzanine on top.

Following are the features exposed by this device in addition to the
Stinger96 board:

* WiFi/BT
* CCS811 VOC sensor
* 2x Digital microphones IM69D130
* 12x WS2812B LEDs

Following peripherals are tested and known to work:

* WiFi/BT
* CCS811

More information about this device can be found in Shiratech website:
https://www.shiratech-solutions.com/products/iot-box/

Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>