driver: adc: npcx: replace constant value with DT_INST_PROP_LEN macro.

In this CL, instead of a constant value, we use the length of property
'pinctrl-0' of adc0 to indicate the number of ADC channels in different
npcx series.

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