drivers: sensors: add driver for the magnetometer in lsm9ds1

This driver supports the magnetometer in the ST lsm9ds1 sensor, on the
I2C bus.
This driver does not support the triggers.
This driver use the stmemsc HAL.

link: https://www.st.com/resource/en/datasheet/lsm9ds1.pdf



Signed-off-by: Miguel Gazquez <miguel.gazquez@bootlin.com>