ana_cmpr_config_t::ref_src field

Reference signal source of the comparator, select using ANA_CMPR_REF_SRC_INTERNAL or ANA_CMPR_REF_SRC_EXTERNAL. For internal reference, the reference voltage should be set to `internal_ref_volt`, for external reference, the reference signal should be connect to `ANA_CMPRx_EXT_REF_GPIO`