iio: imu: bmi270: Remove unused FREQUENCY / SCALE attributes

These attributes are not currently wired up, and will always return
EINVAL.

Fixes: 3ea51548 ("iio: imu: Add i2c driver for bmi270 imu")
Signed-off-by: Justin Weiss <justin@justinweiss.com>
Link: https://patch.msgid.link/20241020220011.212395-2-justin@justinweiss.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>