greybus: arche-platform: Add missing of_node_put() in arche_platform_change_state()

This node pointer is returned by of_find_compatible_node() with
refcount incremented in this function. of_node_put() on it before
exitting this function.

This is detected by Coccinelle semantic patch.

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>