mm/memdump: dynamic turn on backtrace in heap when enable DEBUG_MM

default turn off.
turn on: echo on > /proc/memdump
turn off: echo off > proc/memdump

Signed-off-by: Jiuzhu Dong <dongjiuzhu1@xiaomi.com>

include/nuttx/fs/procfs.h

@@ -133,6 +133,14 @@ struct procfs_meminfo_entry_s
   FAR const char *name;
   FAR struct mm_heap_s *heap;
   struct procfs_meminfo_entry_s *next;
+#if defined(CONFIG_DEBUG_MM)
+
+  /* This is dynamic control flag whether to turn on backtrace in the heap,
+   * you can set it by /proc/memdump.
+   */
+
+  bool backtrace;
+#endif
 };
 
 /****************************************************************************