bus: mvebu: add missing of_node_put() to fix reference leak

Add of_node_put to properly decrement the refcount when we are
done using a given node.

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Reviewed-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

Conflicts:
	drivers/bus/mvebu-mbus.c