Platform: create, use common secure linker script

Create a common linker script and scatter file for secure
binary. This can be used by any platform that has no special
requirements or limitations.
All platforms can specify in their respective cmake files
if they use the common file or want to use a different one.

Signed-off-by: Miklos Balint <miklos.balint@arm.com>
Change-Id: I47b317daca1194878fbf4d48096588c85fadcb23