[Kconfig] Use 256 as the default stack size for idle thread.

src/KConfig

@@ -56,10 +56,10 @@ config RT_USING_HOOK
     default y
     help
         Enable the hook function when system running, such as idle thread hook, thread context switch etc.
-        
+
 config IDLE_THREAD_STACK_SIZE
-    int "The stack size of IDLE thread"
-    default 1024  
+    int "The stack size of idle thread"
+    default 256
 
 config RT_USING_TIMER_SOFT
     bool "Enable software timer with a timer thread"