drivers: imu: adis16475.c: Remove scan index from delta channels

drivers: imu: adis16475.c: Remove scan index from delta channels

Some devices do not support delta angle and delta velocity
burst readings, which means there should be no buffer support
for these types of channels.
A new list of channels is created which contains the delta
channels structures with the scan index equal to -1 to allow
for raw register readings, without buffer support.
This list of channels is assigned to the devices which
do not support delta angle and delta velocity burst
readings.

Fixes: 8f6bc87d67c0 ("iio: imu: adis16475.c: Add delta angle and delta velocity channels")
Signed-off-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20231012122456.765709-2-ramona.gradinariu@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>