staging: octeon: Use 'for_each_child_of_node'

Use 'for_each_child_of_node' instead of hand writing it.
This saves a few line of code.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/eaffe388e6c51e97caf3e8fa474de74428575455.1618920182.git.christophe.jaillet@wanadoo.fr


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>