[CM3] Systick Add helper function to easily set the desired frequency

Add helper function to configure systick to fire at the desired rate. The function selects the /8 prescaler automatically if needed

Usage (for the F4 CPU running at 168MHz, for run systick at rate 100Hz):

```
systick_set_frequency(100, 168000000);
systick_interrupt_enable();
systick_counter_enable();
```

function will return false, if desired rate cannot be reached.