Improve sam_cyutils._dynamic_binary_number_at_fobs_2pwl --- remove for-loop over frequencies

[lzkelley]

Currently there is a for-loop over frequencies, at each integration step. This shouldn't be necessary as we should be able to continually walk through the target frequencies while we iterate over integration steps. The loop currently breaks out when the target frequencies are outside of the steps, so the redundancy isn't horrific, but it could still be improved significantly.

See this section of code.