SPM: Update thread state naming

The thread state THRD_STATE_RUNNING is actually used as runnable.
For example, in the tfm_event_wake() function, a thread woke up by
an event is only becoming runnable. Whether to make it as the current
running thread is decided by scheduler with other condition checks
such as priority - only the thread has highest priority in the runnable
list can run.
The current running thread is indicated by CURR_THRD.

This patch updates the naming to reflect the actual implementation.
Also moves some static functions to caller to simply the code.

Change-Id: Ib8c843c85feff35d6d6287bf82093801e3168e80
Signed-off-by: Kevin Peng <kevin.peng@arm.com>
diff --git a/secure_fw/spm/cmsis_psa/tfm_thread.h b/secure_fw/spm/cmsis_psa/tfm_thread.h
index 925967b..8e96e3f 100644
--- a/secure_fw/spm/cmsis_psa/tfm_thread.h
+++ b/secure_fw/spm/cmsis_psa/tfm_thread.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2020, Arm Limited. All rights reserved.
+ * Copyright (c) 2018-2021, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  *
@@ -14,7 +14,7 @@
 
 /* State code */
 #define THRD_STATE_CREATING       0
-#define THRD_STATE_RUNNING        1
+#define THRD_STATE_RUNNABLE       1
 #define THRD_STATE_BLOCK          2
 #define THRD_STATE_DETACH         3
 #define THRD_STATE_INVALID        4
@@ -170,15 +170,15 @@
  * Return :
  *  Current running thread context pointer.
  */
-struct tfm_core_thread_t *tfm_core_thrd_get_curr_thread(void);
+struct tfm_core_thread_t *tfm_core_thrd_get_curr(void);
 
 /*
- * Get next running thread in list.
+ * Get next thread to run in list.
  *
  * Return :
- *  Pointer of next thread to be run.
+ *  Pointer of next thread to run.
  */
-struct tfm_core_thread_t *tfm_core_thrd_get_next_thread(void);
+struct tfm_core_thread_t *tfm_core_thrd_get_next(void);
 
 /*
  * Start scheduler for existing threads