coresight: hwevent: Add snapshot of Coresight HWEVENT driver

This is a snapshot of the coresight-hwevent driver as of msm-4.9
commit 'ac8f754d2246963e20623f7ee08eb9f94df0605a'(coresight: hwevent:
Change naming convention for clock).

Change-Id: Ia5bf274e6b4da1f9825695f1bedf47d859d6a101
Signed-off-by: Rama Aparna Mallavarapu <aparnam@codeaurora.org>