Make use of the __free() cleanup handler to automatically free nodes
when they get out of scope. Only the probe function is affected by this
modification.

Given that this mechanism requires the node to be initialized, its
initialization and the value check have been moved to the top of the
function.

After removing uses of of_node_put(), the jump to out_put_np is no
longer necessary.
Suggested-by: Julia Lawall <julia.lawall@inria.fr>
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>