Add a convenience macro to iterate over subnodes of a node. Make use of
this where appropriate in the code.
Change-Id: Iae0fb554472d0b5819d26becbbcf8909ff891514
Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
(cherry picked from commit 3991f42ed2e38aff28ba3c24369bfbd90620bea7)