coresight: Remote-etm: Add snapshot of Remote ETM driver

This is a snapshot of the coresight-remote-etm driver as of msm-4.9
commit '18dfa88167604e855832b7ab0be576745bfecd65'(coresight: Remote-etm:
Add remote etm driver support in upstream code).

Change-Id: I0e145d65d0f7155b623e2a79e46fe3ae649a2ee3
Signed-off-by: Rama Aparna Mallavarapu <aparnam@codeaurora.org>