clk: qcom: clk-debug: Fix clk measurement algorithm

Due to measurement counter does not self-clear reliably, explicitly
clearing CLR_CNT in SW instead of relying on self-clear HW sequence.
SW/HW CLR_CNT enable and disable sequence requires ~1us delay to allow
clearing the count.
Increasing sample rate to 27ms to get more accurate measurement for low
frequency clocks which allows to keep logic simpler than implementing
different logic for higher vs slows clocks with respect to sample rate.

Change-Id: I054083358305124406294511b2d03554ee586557
Signed-off-by: Vivek Aknurwar <viveka@codeaurora.org>