SST: Implement PSA SST API for secure partitions

This patch implements PSA SST API to be called from secure partitions.
It also updates the secure test suits to use the PSA SST API instead
the veneers APIs.

Change-Id: Ib048c4eb6c791ea741c0f7e0ce55e93c888f0c8e
Signed-off-by: Marc Moreno <marc.morenoberengue@arm.com>
diff --git a/interface/include/tfm_sst_veneers.h b/interface/include/tfm_sst_veneers.h
index c13c2cc..df62f75 100644
--- a/interface/include/tfm_sst_veneers.h
+++ b/interface/include/tfm_sst_veneers.h
@@ -83,7 +83,11 @@
 /**
  * \brief Reads asset's data from asset referenced by asset UUID.
  *
- * \param[in]     client_id   Client ID which calls the service
+
+ * \param[in]     client_id   Client ID which calls the service.
+ *                            In case, the caller is a secure partition, this
+ *                            parameter can be a non-secure or secure client ID
+ *                            if the read is in behalf of that client.
  * \param[in]     asset_uuid  Asset UUID
  * \param[in]     s_token     Pointer to the asset's token
  *                            \ref tfm_sst_token_t