Function esp_idf_sys::spi_get_actual_clock

pub unsafe extern "C" fn spi_get_actual_clock(
    fapb: c_int,
    hz: c_int,
    duty_cycle: c_int,
) -> c_int

@brief Calculate the working frequency that is most close to desired frequency.

@param fapb The frequency of apb clock, should be APB_CLK_FREQ. @param hz Desired working frequency @param duty_cycle Duty cycle of the spi clock

@return Actual working frequency that most fit.