SPM: Add non-secure context management support

This patch adds the support for non-secure context management.
It will be further used by the non-secure client extension to manage the
non-secure client ID.

Signed-off-by: David Wang <david.wang@arm.com>
Change-Id: I5b3ea60d52f71e82eb1d7ed4de94f92122e6b877
3 files changed