coresight: add support for cti save disable

Add support to disable CTI save and restore to avoid voting for
CTI clock during probe as well as the associated save and restore
latency at the cost of breaking cpu CTI support on targets where
cpu CTIs have to be preserved across power collapse.

This allows for low overhead CTI support where cpu CTI usage is
not required but the target requires cpu CTIs to be preserved
across power collapse.

Change-Id: I0545d3442d1d6b2f707da7f56d029a7df2f7cae9
Signed-off-by: Pratik Patel <pratikp@codeaurora.org>