iio: adc: cpcap-adc: Demote seemingly unintentional kerneldoc header

iio: adc: cpcap-adc: Demote seemingly unintentional kerneldoc header

None of the headers demoted here provide any descriptions.

Fixes the following W=1 kernel build warning(s):

 drivers/iio/adc/cpcap-adc.c:100: warning: Function parameter or member 'ato_in' not described in 'cpcap_adc_ato'
 drivers/iio/adc/cpcap-adc.c:100: warning: Function parameter or member 'atox_in' not described in 'cpcap_adc_ato'
 drivers/iio/adc/cpcap-adc.c:100: warning: Function parameter or member 'adc_ps_factor_in' not described in 'cpcap_adc_ato'
 drivers/iio/adc/cpcap-adc.c:100: warning: Function parameter or member 'atox_ps_factor_in' not described in 'cpcap_adc_ato'
 drivers/iio/adc/cpcap-adc.c:100: warning: Function parameter or member 'ato_out' not described in 'cpcap_adc_ato'
 drivers/iio/adc/cpcap-adc.c:100: warning: Function parameter or member 'atox_out' not described in 'cpcap_adc_ato'
 drivers/iio/adc/cpcap-adc.c:100: warning: Function parameter or member 'adc_ps_factor_out' not described in 'cpcap_adc_ato'
 drivers/iio/adc/cpcap-adc.c:100: warning: Function parameter or member 'atox_ps_factor_out' not described in 'cpcap_adc_ato'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_AD0' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_BATTP' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_VBUS' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_AD3' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_BPLUS_AD4' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_CHG_ISENSE' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_BATTI' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_USB_ID' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_AD8' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_AD9' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_LICELL' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_HV_BATTP' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_TSX1_AD12' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_TSX2_AD13' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_TSY1_AD14' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_TSY2_AD15' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_BATTP_PI16' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_BATTI_PI17' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:153: warning: Enum value 'CPCAP_ADC_CHANNEL_NUM' not described in enum 'cpcap_adc_channel'
 drivers/iio/adc/cpcap-adc.c:165: warning: Enum value 'CPCAP_ADC_TIMING_IMM' not described in enum 'cpcap_adc_timing'
 drivers/iio/adc/cpcap-adc.c:165: warning: Enum value 'CPCAP_ADC_TIMING_IN' not described in enum 'cpcap_adc_timing'
 drivers/iio/adc/cpcap-adc.c:165: warning: Enum value 'CPCAP_ADC_TIMING_OUT' not described in enum 'cpcap_adc_timing'

Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>