libbladeRF: Fix frequency selection clamping.

While clamping the minimum values for the frequency selection, the
lowest value was being set but not checked against.

Also modify the range table to use the enumerations for lowest and
highest frequency for consistency.
cli: Print the actual frequency set.

Since bladerf_set_frequency() does not return an actual value set
and may clamp the requested frequency, cause the CLI to query the
currently set frequency and print that out to avoid confusion.