remove debugfs_get_dentry function

debugfs_create_dir("ktap") is moved into modules init,
so there won't have debugfs dir cannot remove issue.
support all event traceing

os.trace("", f)
(not try to use like this now, there will hang now, fix it in future)
add percpu variable percpu_trace_iterator

don't need kmalloc trace_iterator every time when
event_annotate called