Replace Nuvoton NPCX series definitions with new Kconfig definitions in
the npcx drivers. The benefit of this approach is that we won't touch
the npcx driver sources again during introducing a new npcx series next
time.

Signed-off-by: Mulin Chao <mlchao@nuvoton.com>

Update adc drivers to use DT_HAS_<compat>_ENABLED Kconfig symbol
to expose the driver and enable it by default based on devicetree.

We remove 'depend on' Kconfig for symbols that would be implied by
the devicetree node existing.

Signed-off-by: Kumar Gala <galak@kernel.org>

Fixed typo in Kconfig.npcx files.

Signed-off-by: Mulin Chao <mlchao@nuvoton.com>

NPCX7 includes a 10-bit resolution Analog-to-Digital Converter (ADC). Up
to 10 voltage inputs can be measured and a internal voltage reference
(VREF), 2.816V (typical) is used for measurement. It can be triggered
automatically in Autoscan mode. Each input channel is assigned a
separate result register, which is updated at the end of the conversion.

The CL also includes:
— Add npcx adc device tree declarations.
— Zephyr adc api implementation.
— Add adc definitions of npcx7 in
  tests/drivers/adc/adc_api/src/test_adc.c for supporting test suites.

Signed-off-by: Mulin Chao <MLChao@nuvoton.com>