hla: Add Simulated DCC register for target communicaton

Change-Id: I193be169059caba661e46de8081d7e92f92cafee
Signed-off-by: Brent Roman <brent@mbari.org>
Reviewed-on: http://openocd.zylin.com/1364
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>