PlatformSP: Add Platform service

TF-M Platform service is a trusted service which allows secure
partitions and non-secure applications to interact with some
platform-specific components. There are a number of features which
requires some interaction with platform-specific components which
are at the same time essential for the security of the system.
Therefore, those components need to be handled by a secure partition
which is part of the trusted compute base.

This patch adds the Platform service which provides the system reset
as a first function.

Change-Id: I68253328db22a45fb6a3d6820dd85b1e24ea96f0
Signed-off-by: Marc Moreno <marc.morenoberengue@arm.com>
43 files changed