add i2c controller support to st_lsm6dsx driver

Introduce i2c controller support to st_lsm6dsx driver for lsm6dso sensor. st_lsm6dsx sensor-hub supports up to 3 concurrent slave devices. Add register map for lis2mdl magnetometer sensor.
Add hw FIFO support to st_lsm6dsx sensorhub driver.

Changes since v1:
- move back st_lsm6dsx_set_fifo_mode routine in fifo_lock critical section in st_lsm6dsx_flush_fifo
- improve documentation
- move st_lsm6dsx_sensor_set_enable definition in a separated patch
- move st_lsm6dsx_push_tagged_data definition in a separated patch
- use proper ts_ref for ext devices in st_lsm6dsx_push_tagged_data
- fix invalid iio_dev identification in st_lsm6dsx_push_tagged_data when ST_LSM6DSX_EXT1_TAG is read from the FIFO
- refactor st_lsm6dsx_shub_probe moving wai check in a dedicated routine
- fix abi issue in scale_available definition

Lorenzo Bianconi (9):
iio: imu: st_lsm6dsx: introduce locked read/write utility routines
iio: imu: st_lsm6dsx: reload trimming parameter at bootstrap
iio: imu: st_lsm6dsx: remove static from st_lsm6dsx_set_watermark
iio: imu: st_lsm6dsx: introduce ST_LSM6DSX_ID_EXT sensor ids
iio: imu: st_lsm6dsx: introduce st_lsm6dsx_sensor_set_enable routine
iio: imu: st_lsm6dsx: add i2c embedded controller support
iio: imu: st_lsm6dsx: add st_lsm6dsx_push_tagged_data routine
iio: imu: st_lsm6dsx: add hw FIFO support to i2c controller
dt-bindings: iio: imu: st_lsm6dsx: add support to i2c pullup resistors

 .../bindings/iio/imu/st_lsm6dsx.txt           |   1 +
 drivers/iio/imu/st_lsm6dsx/Makefile           |   3 +-
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h       | 167 +++-
 .../iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c    | 165 ++--
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c  | 283 +++++--
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c  | 777 ++++++++++++++++++
 .../linux/platform_data/st_sensors_pdata.h    |   2 +
 7 files changed, 1263 insertions(+), 135 deletions(-)
 create mode 100644 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c

2.19.1