stmhal/main: Use _estack value to initialise stack extents.

stmhal/main.c

@@ -508,8 +508,8 @@ soft_reset:
     // Stack limit should be less than real stack size, so we have a chance
     // to recover from limit hit.  (Limit is measured in bytes.)
     // Note: stack control relies on main thread being initialised above
-    mp_stack_ctrl_init();
-    mp_stack_set_limit((char*)&_ram_end - (char*)&_heap_end - 1024);
+    mp_stack_set_top(&_estack);
+    mp_stack_set_limit((char*)&_estack - (char*)&_heap_end - 1024);
 
     // GC init
     gc_init(&_heap_start, &_heap_end);