Enable Zephyr dynamic stack threads

Enable Zephyr dynamic stack posix threading, with stack pool of 4 and
stack size of 4096.

TG-553

openrtx/src/core/threads.c

@@ -189,13 +189,15 @@ void *rtx_threadFunc(void *arg)
  */
 void create_threads()
 {
+    pthread_t rtx_thread;
+    pthread_t ui_thread;
+
     // Create RTX state mutex
     pthread_mutex_init(&rtx_mutex, NULL);
 
+#ifndef __ZEPHYR__
     // Create rtx radio thread
-    pthread_t      rtx_thread;
     pthread_attr_t rtx_attr;
-
     pthread_attr_init(&rtx_attr);
     pthread_attr_setstacksize(&rtx_attr, RTX_TASK_STKSIZE);
 
@@ -209,10 +211,13 @@ void create_threads()
     pthread_create(&rtx_thread, &rtx_attr, rtx_threadFunc, NULL);
 
     // Create UI thread
-    pthread_t      ui_thread;
     pthread_attr_t ui_attr;
-
     pthread_attr_init(&ui_attr);
     pthread_attr_setstacksize(&ui_attr, UI_TASK_STKSIZE);
     pthread_create(&ui_thread, &ui_attr, ui_threadFunc, NULL);
+#else
+    // On zephyr just spawn the threads without setting the attributes
+    pthread_create(&rtx_thread, NULL, rtx_threadFunc, NULL);
+    pthread_create(&ui_thread, NULL, ui_threadFunc, NULL);
+#endif
 }

platform/targets/ttwrplus/ttwrplus_defconfig

@@ -3,3 +3,8 @@ CONFIG_BOOTLOADER_MCUBOOT=y
 CONFIG_DISPLAY=y
 CONFIG_SSD1306=y
 CONFIG_SSD1306_SH1106_COMPATIBLE=y
+CONFIG_THREAD_STACK_INFO=y
+CONFIG_DYNAMIC_THREAD=y
+CONFIG_DYNAMIC_THREAD_STACK_SIZE=4096
+CONFIG_DYNAMIC_THREAD_PREFER_POOL=y
+CONFIG_DYNAMIC_THREAD_POOL_SIZE=4