multisynth_calc when r_div applied

[mrguen]

In the multisynth_calc(uint64_t freq, uint64_t pll_freq, struct Si5351ARegSet *reg)

There is a test if the frequency is under Si5351A_MULTISYNTH_MIN_FREQ * Si5351A_FREQ_MULT and setting it to this min value.

This makes all output for frequencies under Si5351A_MULTISYNTH_MIN_FREQ * Si5351A_FREQ_MULT the same and wrong.

I think the code should be

if (freq < Si5351A_MULTISYNTH_MIN_FREQ * Si5351A_FREQ_MULT)
{
    freq = select_r_div(&freq) * freq;
}