iio: inv_mpu6050: Fully validate gyro and accel scale writes

iio: inv_mpu6050: Fully validate gyro and accel scale writes

When setting the gyro or accelerometer scale the inv_mpu6050 driver ignores
the integer part of the value. As a result e.g. all of 0.13309, 1.13309,
12345.13309, ... are accepted as a valid gyro scale and 0.13309 is the
scale that gets set in all those cases.

Make sure to check that the integer part of the scale value is 0 and reject
it otherwise.

Fixes: 09a642b78523 ("Invensense MPU6050 Device Driver.")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Link: https://lore.kernel.org/r/20210405114441.24167-1-lars@metafoo.de
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>