Core: Thread structure refine

- Change the thread context structure name from 'struct tfm_thrd_ctx' to
  'struct tfm_core_thread_t'.
- Change the thread context structure member from 'status' to 'state' to
  indicate the state machine of thread better.
- Add 'core' prefix of thread functions to indicate that these functions
  are under core scope.

Change-Id: I642956f4dde0c7cf9e0f98fbb3c670335d1b85de
Signed-off-by: Summer Qin <summer.qin@arm.com>
diff --git a/secure_fw/spm/spm_api.h b/secure_fw/spm/spm_api.h
index fbcda09..a99033a 100644
--- a/secure_fw/spm/spm_api.h
+++ b/secure_fw/spm/spm_api.h
@@ -91,7 +91,7 @@
     struct tfm_event_t signal_evnt;     /* Event signal                      */
     uint32_t signals;                   /* Service signals had been triggered*/
     struct tfm_list_node_t service_list;/* Service list                      */
-    struct tfm_thrd_ctx sp_thrd;        /* Thread context                    */
+    struct tfm_core_thread_t sp_thrd;   /* Thread object                     */
     uint32_t assigned_signals;          /* All assigned signals              */
 #else /* TFM_PSA_API */
     uint32_t partition_state;