of: Fix a refcounting bug in __of_attach_node_sysfs()

The problem in this code is that if kobject_add() fails, then it should
call of_node_put(np) to drop the reference count.  I've actually moved
the of_node_get(np) later in the function to avoid needing to do clean
up.

Fixes: 5b2c2f5a ("of: overlay: add missing of_node_get() in __of_attach_node_sysfs")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Rob Herring <robh@kernel.org>