powerpc/pseries: dynamically added OF nodes need to call of_node_init

Commit 75b57ecf refactored device tree nodes to use kobjects such that they
can be exposed via /sysfs. A secondary commit 0829f6d1 furthered this rework
by moving the kobect initialization logic out of of_node_add into its own
of_node_init function. The inital commit removed the existing kref_init calls
in the pseries dlpar code with the assumption kobject initialization would
occur in of_node_add. The second commit had the side effect of triggering a
BUG_ON during DLPAR, migration and suspend/resume operations as a result of
dynamically added nodes being uninitialized.

This patch fixes this by adding of_node_init calls in place of the previously
removed kref_init calls.

Fixes: 0829f6d1 ("of: device_node kobject lifecycle fixes")
Cc: stable@vger.kernel.org
Signed-off-by: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>
Acked-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Acked-by: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>