lisa.analysis.frequency: Fix df_cpu_frequency()
lisa.analysis.frequency: Fix df_cpu_frequency()

* Only require one of cpu_frequency, userspace@cpu_frequency_devlib
* Fix typo in reference to userspace@cpu_frequency_devlib
* Fix wrong column names

credp/lisa,credp/lisa,credp/lisa,ARM-software/lisa,ARM-software/lisa,ARM-software/lisa,credp/lisa,ARM-software/lisa