drivers/sensor: add support to IIS2MDC magnetometer sensor

The IIS2MDC is a 3D digital magnetometer ultra-low power sensor
for industrial applications, which can be interfaced through
either I2C or SPI bus.

https://www.st.com/resource/en/datasheet/iis2mdc.pdf



This driver is based on stmemsc i/f v1.02.

Signed-off-by: Armando Visconti <armando.visconti@st.com>