iio: imu: st_lsm6dsx: add i3c basic support for LSM6DSO and LSM6DSR

For today the st_lsm6dsx driver support LSM6DSO and LSM6DSR sensor only in
spi and i2c mode.

The LSM6DSO and LSM6DSR are also i3c capable so let's give i3c support to
them.

Signed-off-by: Vitor Soares <vitor.soares@synopsys.com>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

treewide: Add SPDX license identifier - Makefile/Kconfig

Add SPDX license identifiers to all Make/Kconfig files which:

- Have no license information of any form

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

iio: imu: st_lsm6dsx: add i2c embedded controller support

i2c controller embedded in lsm6dx series can connect up to four
slave devices using accelerometer sensor as trigger for i2c
read/write operations.
Introduce sensor hub support for lsm6dso sensor. Add register map
for lis2mdl magnetometer sensor.
In order to perform single read/write operations st_lsm6dsx driver
relies on SLV0 channel (hw FIFO is not supported yet)

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: imu: add support to lsm6dsx driver

Add support to STM LSM6DS3-LSM6DSM 6-axis (acc + gyro) Mems sensor

http://www.st.com/resource/en/datasheet/lsm6ds3.pdf
http://www.st.com/resource/en/datasheet/lsm6dsm.pdf

- continuous mode support
- i2c support
- spi support
- sw fifo mode support
- supported devices: lsm6ds3, lsm6dsm

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@st.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>