Use helper function for_each_child_of_node_scoped()

Merge series from Ai Chao <aichao@kylinos.cn>:

This patch series introduces wrapper functions for_each_child_of_node_scoped().

The for_each_child_of_node_scoped() helper provides a scope-based clean-up
functionality to put the device_node automatically, and as such, there is
no need to call of_node_put() directly.