drivers: sensor: Add adc-comparator binding and implementation for NPCX

Comparator will monitor signal though ADC channel, based on
user configuration, callback will be triggered.
This will enable comparator functionality for nuvoton MCU utilizing its
ADC threshold detection feature. Implementation is exported through
sensor trigger API. Use of CONFIG_ADC_CMP_NPCX is required.

Signed-off-by: Bernardo Perez Priego <bernardo.perez.priego@intel.com>