DPE: Rename DeriveChild to DeriveContext

As per spec updates in v1.0 r9:
* Rename DeriveChild to DeriveContext.
* Rename its input argument allow_child_to_derive to
  allow_new_context_to_derive.

Also, update the context manager code to NOT preallocate the slot for
subsequent derivation request. Rather allocate and use the slot
as and when the request is made.

Signed-off-by: Maulik Patel <maulik.patel@arm.com>
Change-Id: I44ed2f54d8039b6326780f60b15d560453356e56
diff --git a/partitions/dice_protection_environment/dpe_log.h b/partitions/dice_protection_environment/dpe_log.h
index 9061e27..1f08e94 100644
--- a/partitions/dice_protection_environment/dpe_log.h
+++ b/partitions/dice_protection_environment/dpe_log.h
@@ -23,14 +23,14 @@
 void log_derive_rot_context(const DiceInputValues *dice_inputs);
 
 /**
- * \brief Log the derive child command parameters.
+ * \brief Log the derive context command parameters.
  */
-void log_derive_child(int context_handle,
-                      bool retain_parent_context,
-                      bool allow_child_to_derive,
-                      bool create_certificate,
-                      const DiceInputValues *dice_inputs,
-                      int32_t client_id);
+void log_derive_context(int context_handle,
+                        bool retain_parent_context,
+                        bool allow_new_context_to_derive,
+                        bool create_certificate,
+                        const DiceInputValues *dice_inputs,
+                        int32_t client_id);
 
 /**
  * \brief Log the destroy context command parameters.
@@ -64,7 +64,7 @@
 #else /* TFM_PARTITION_LOG_LEVEL */
 
 #define log_derive_rot_context(...)
-#define log_derive_child(...)
+#define log_derive_context(...)
 #define log_destroy_context(...)
 #define log_certify_key(...)
 #define log_intermediate_certificate(...)