coresight: revert to map/unmap based clock usage for cti driver

This reverts commit 8b4b8aff with
merge conflict resolutions.

CTI clock is required to be on for the CTI to pass the cross
trigger events and hence the revert to voting for clocks as part
of the first map on a CTI and unvoting the clocks as part of the
last unmap on a CTI.

Change-Id: I98901443c6526e223853403e2ff1a0eea2adbf83
Signed-off-by: Pratik Patel <pratikp@codeaurora.org>