nanohub: new variant "argonkey"

ST sensor hub mezzanine compatible with "Low speed expansion
connector" of Linaro 96board specifications
- Consumer Edition (CE);
- Enterprise Edition (EE);
- IoT Edition (IE) only for 1.8V version.

Hardware list:
- CPU: STM32F412CG
- NOR Flash: 1024 KB
- SRAM: 256 KB
- RTC crystal for accurate time-stamping
- Accel/Gyro + Geomagnetic sensors: ST LSM6DSL + ST LIS2MDL
- Pressure/Temp sensor: ST LPS22HB
- Humidity sensor: ST HTS221
- Proximity sensor: ST VL53L0X
- ALS sensor: Intersil ILS29034
- Hall sensor: Murata MRMS501A
- MEMS digital microphone: ST MP34DT05
- LED driver with 16 LEDs: TI LP3943
- Two GPIO-driven LEDs
- I2C EEPROM for board detection: ST M24C02-F

No driver for proximity sensor and microphone in this commit.
EEPROM is managed by host only so no need for any support in
argonkey firmware.

Change-Id: I10b4b60c2596b7734135243d45857fc9a08c3b9f
Signed-off-by: Antonio Borneo <antonio.borneo@st.com>
13 files changed