This introduces the "freqmon" command, provided that FREQUENCY_MONITOR option in the Kconfig is enabled.

Typical use cases are:

wrc# freqmon
Dumps current frequencies of all clocks used by the WRC (REF, DMTD, SYS, AUX, EXT).

wrc# freqmon checkvco [n_steps]
Measures the tuning/pull range of all VCOs. The optional n_steps parameter defines how many intermediate
tuning DAC values are taken during characterization.