cpufreq: qcom-hw: add cycle counter support

The scheduler needs a way to track cpu cycle counts,
return the total cycle count by adding the difference between
the current cycle count and the previous from reading the EPSS
cycle counters.

Change-Id: Ifacdb0fe8fb9c692322d3ef7fcd25c6c5d5cd4f3
Signed-off-by: David Dai <daidavid1@codeaurora.org>