iio: adc: imx8qxp: Fix address for command buffer registers

The ADC Command Buffer Register high and low are currently pointing to
the wrong address and makes it impossible to perform correct
ADC measurements over all channels.

According to the datasheet of the imx8qxp the ADC_CMDL register starts
at address 0x100 and the ADC_CMDH register starts at address 0x104.

This bug seems to be in the kernel since the introduction of this
driver.

This can be observed by checking all raw voltages of the adc and they
are all nearly identical:

cat /sys/bus/iio/devices/iio\:device0/in_voltage*_raw
3498
3494
3491
3491
3489
3490
3490
3490

Fixes: 1e23dcaa

 ("iio: imx8qxp-adc: Add driver support for NXP IMX8QXP ADC")
Signed-off-by: Philipp Rossak <embed3d@gmail.com>
Acked-by: Haibo Chen <haibo.chen@nxp.com>
Link: https://lore.kernel.org/r/20230904220204.23841-1-embed3d@gmail.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>