coresight: add the authentication logic for coresight etm

Add the authentication logic that depends on the CoreSight AUTHSTATUS
register rather than the fuses that helps in collecting the CPU trace
on the secure device if ETM is functional.

Change-Id: I7ca410cc7b72a98235101f64f090c65e37603d27
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>