iio: adis16400: Set timestamp as the last element in chan_spec

This is necessary since timestamp is calculated as the last element
in iio_compute_scan_bytes().

Without this fix any userspace code reading the layout of the buffer via
sysfs will incorrectly interpret the data leading some nasty corruption.

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: stable@vger.kernel.org
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/imu/adis16400.h b/drivers/iio/imu/adis16400.h
index 2f8f9d6..0916bf6 100644
--- a/drivers/iio/imu/adis16400.h
+++ b/drivers/iio/imu/adis16400.h
@@ -189,6 +189,7 @@
 	ADIS16300_SCAN_INCLI_X,
 	ADIS16300_SCAN_INCLI_Y,
 	ADIS16400_SCAN_ADC,
+	ADIS16400_SCAN_TIMESTAMP,
 };
 
 #ifdef CONFIG_IIO_BUFFER