hvc_dcc: Add support for arm64 cpus

Split out the architecture debug channel register
reads/writes to arch specifc header files and add
support for arm64 dcc operations.

Change-Id: I48df3a1470760ebaa57eafd5a1f3e8cc9c7bd826
Signed-off-by: Abhimanyu Kapur <abhimany@codeaurora.org>