se-proxy: Add proxy service list

Add a "linker constructed array" for service proxy factory functions.
The solution allows splitting the proxy SP initialization code to
service specific pieces, and to enable or disable a service by adding or
removing the relevant C file from the build.

Signed-off-by: Gyorgy Szing <gyorgy.szing@arm.com>
Change-Id: I6d561e8b769f409ce5577f34cd79cd4f5d3b119f
3 files changed