SPM: Introduce ns_agent partition flag

Add support for an optional boolean "ns_agent" in the manifest file,
which sets a partition flag.
Change IS_PARTITION_NS_AGENT to examine the flag.
Remove TFM_SP_NON_SECURE_ID.

Signed-off-by: Chris Brand <chris.brand@cypress.com>
Change-Id: Ia4b4d8d9a5b27f9baab28971b365fe5f35cd9694
8 files changed