scripts/gdb: add iteration function for rbtree

Add inorder iteration function for rbtree usage.

This is a preparation patch for the next patch to fix the gdb mounts
issue.

Link: https://lkml.kernel.org/r/[e-mail]
Fixes: 2eea9ce4310d ("mounts: keep list of mounts in an rbtree")
Signed-off-by: Kuan-Ying Lee <[e-mail]>
Cc: Jan Kiszka <[e-mail]>
Cc: Kieran Bingham <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

scripts/gdb/linux/rbtree.py

···
 rb_root_type = utils.CachedType("struct rb_root")
 rb_node_type = utils.CachedType("struct rb_node")
 
+def rb_inorder_for_each(root):
+    def inorder(node):
+        if node:
+            yield from inorder(node['rb_left'])
+            yield node
+            yield from inorder(node['rb_right'])
+
+    yield from inorder(root['rb_node'])
+
+def rb_inorder_for_each_entry(root, gdbtype, member):
+    for node in rb_inorder_for_each(root):
+        yield utils.container_of(node, gdbtype, member)
 
 def rb_first(root):
     if root.type == rb_root_type.get_type():