drivers/iio: Remove all strcpy() uses

strcpy() performs no bounds checking on the destination buffer. This
could result in linear overflows beyond the end of the buffer, leading
to all kinds of misbehaviors. So, remove all the uses and add
devm_kstrdup() or devm_kasprintf() instead.

Also, modify the "for" loop conditions to clarify the access to the
st->orientation.rotation buffer.

This patch is an effort to clean up the proliferation of str*()
functions in the kernel and a previous step in the path to remove
the strcpy function from the kernel entirely [1].

[1] https://github.com/KSPP/linux/issues/88

Signed-off-by: Len Baker <len.baker@gmx.com>
Link: https://lore.kernel.org/r/20210815174204.126593-1-len.baker@gmx.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: imu: inv_mpu6050: fix data polling interface

When reading data with the polling interface, we need to wait
at 1 sampling period to have a sample.
For gyroscope and magnetometer, we need to wait for 2 periods
before having a correct sample.

Not suitable for stable or backporting.

Signed-off-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: imu: inv_mpu6050: rewrite power and engine management

Rewrite clock management to use automatic clock switching
present since MPU6500.
Sensors engine management can now turn on or off a batch of
sensors which simplifies usage a lot.
Temperature sensor is now turned on/off depending on usage.

Signed-off-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: imu: inv_mpu6050: simplify polling magnetometer

Do not change the sampling rate value. Let userspace decide what
is the sampling rate to use.
Read only the requested axis.

Signed-off-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: imu: inv_mpu6050: add support of MPU9150 magnetometer

Add support for driving MPU9150 magnetometer (AK8975) from mpu.

Signed-off-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: imu: inv_mpu6050: add MPU925x magnetometer support

Add support of driving MPU9250 magnetometer connected on i2c
auxiliary bus using the MPU i2c master.

Signed-off-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>