libs/utils: add frequency plotting for peripheral clocks

Allows the plotting of clocks using the linux common clock tracing
infrastructure tracing. Chart shows the periods the clock is on or
off, as well as frequency information.

Test: run examples/android/workloads/Android_YouTube.ipynb, which
Test: now has a plotPeripheralFrequencies() example
Change-Id: I76b0d7408398a3252a13bc58d9d337e1cccab84e