iio: imu: smi240: add driver

iio: imu: smi240: add driver

add the iio driver for bosch imu smi240. The smi240 is a combined
three axis angular rate and three axis acceleration sensor module
with a measurement range of +/-300°/s and up to 16g. A synchronous
acc and gyro sampling can be triggered by setting the capture bit
in spi read command.

Implemented features:
* raw data access for each axis through sysfs
* tiggered buffer for continuous sampling
* synchronous acc and gyro data from tiggered buffer

Signed-off-by: Shen Jianping <Jianping.Shen@de.bosch.com>
Link: https://patch.msgid.link/20241018135234.5446-3-Jianping.Shen@de.bosch.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>