iio: adc: xilinx-ams: Fixed wrong sequencer register settings

iio: adc: xilinx-ams: Fixed wrong sequencer register settings

Register settings used for the sequencer configuration register
were incorrect, causing some inputs to not be read properly.

Fixes: d5c70627a794 ("iio: adc: Add Xilinx AMS driver")
Signed-off-by: Robert Hancock <robert.hancock@calian.com>
Reviewed-by: Michael Tretter <m.tretter@pengutronix.de>
Acked-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/20220127173450.3684318-4-robert.hancock@calian.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>