coresight-hwevent: Change naming convention for clock

Make use of amba framework naming convention for hw event clock.
With this change we will be setting the clock rate for all devices
as part of coresight register. Clock enable and disable still
follow the existing framework.

Change-Id: I54bcb31db288d3e411bfb5ea0a80fcafdb71512d
Signed-off-by: Satyajit Desai <sadesai@codeaurora.org>