Revert "tls: Move pthread key destructor to libc"

This reverts commit cc514d7791.

* It introduced a regression.
  https://github.com/apache/incubator-nuttx/issues/3868

* It seems conceptually wrong to have per-process data in
  the main thread's stack.

include/nuttx/sched.h

@@ -530,6 +530,14 @@ struct task_group_s
   FAR struct join_s *tg_jointail; /* Tail of a list of join data            */
 #endif
 
+  /* Thread local storage ***************************************************/
+
+#if CONFIG_TLS_NELEM > 0
+  tls_ndxset_t tg_tlsset;                   /* Set of TLS indexes allocated */
+
+  tls_dtor_t  tg_tlsdestr[CONFIG_TLS_NELEM];  /* List of TLS destructors    */
+#endif
+
   /* POSIX Signal Control Fields ********************************************/
 
   sq_queue_t tg_sigactionq;         /* List of actions for signals              */

include/nuttx/tls.h

@@ -118,13 +118,6 @@ struct task_info_s
   struct tls_info_s ta_tls;    /* Must be first field */
 #ifndef CONFIG_BUILD_KERNEL
   struct getopt_s   ta_getopt; /* Globals used by getopt() */
-#endif
-  /* Thread local storage ***************************************************/
-
-#if CONFIG_TLS_NELEM > 0
-  sem_t        ta_tlssem;
-  tls_ndxset_t ta_tlsset;                    /* Set of TLS index allocated  */
-  tls_dtor_t   ta_tlsdtor[CONFIG_TLS_NELEM]; /* List of TLS destructors     */
 #endif
 };
 
@@ -327,20 +320,4 @@ void tls_destruct(void);
 
 FAR struct task_info_s *task_get_info(void);
 
-/****************************************************************************
- * Name: task_setup_info
- *
- * Description:
- *   Setup task_info_s for task
- *
- * Input Parameters:
- *   info - New created task_info_s
- *
- * Returned Value:
- *   OK on success; ERROR on failure
- *
- ****************************************************************************/
-
-int task_setup_info(FAR struct task_info_s *info);
-
 #endif /* __INCLUDE_NUTTX_TLS_H */

include/sys/syscall_lookup.h

@@ -294,6 +294,14 @@ SYSCALL_LOOKUP(telldir,                    1)
   SYSCALL_LOOKUP(shmdt,                    1)
 #endif
 
+#if CONFIG_TLS_NELEM > 0
+  SYSCALL_LOOKUP(tls_alloc,                0)
+  SYSCALL_LOOKUP(tls_free,                 1)
+  SYSCALL_LOOKUP(tls_get_set,              1)
+  SYSCALL_LOOKUP(tls_get_dtor,             1)
+  SYSCALL_LOOKUP(tls_set_dtor,             2)
+#endif
+
 /* The following are defined if pthreads are enabled */
 
 #ifndef CONFIG_DISABLE_PTHREAD