lisa.analysis.frequency: Correct for clock events

Linux kernel doesn't use the events 'clock_set_rate', 'clock_enable' and
'clock_disable' for clock operations; the really used trace events are
'clk_set_rate', 'clk_enable', 'clk_disable'.

This patch uses the appropriate trace events for peripheral clocks.

Signed-off-by: Leo Yan <leo.yan@linaro.org>