Add mm communicate service location strategy

To support service discovery and RPC session extablishment
for SMM services reached via MM Communicate, a new service
location strategy and service context has been added to the
service locator. Client applications that need to use say the
smm-variable service can now use the service locator to
set-up a session.

Signed-off-by: Julian Hall <julian.hall@arm.com>
Change-Id: I4a97af4763c6a48b9dbe2dcf87ec2c79654131de
10 files changed