libnvdimm, of_pmem: use dev_to_node() instead of of_node_to_nid()

Remove the direct dependency on of_node_to_nid() by using dev_to_node()
instead. Any DT platform device will have its NUMA node id set when the
device is created.

With this, commit 291717b6 ("libnvdimm, of_pmem: workaround OF_NUMA=n
build error") can be reverted.

Fixes: 71719760 ("libnvdimm: Add device-tree based driver")
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Oliver O'Halloran <oohall@gmail.com>
Cc: linux-nvdimm@lists.01.org
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/nvdimm/of_pmem.c

@@ -67,7 +67,7 @@ static int of_pmem_region_probe(struct platform_device *pdev)
 		 */
 		memset(&ndr_desc, 0, sizeof(ndr_desc));
 		ndr_desc.attr_groups = region_attr_groups;
-		ndr_desc.numa_node = of_node_to_nid(np);
+		ndr_desc.numa_node = dev_to_node(&pdev->dev);
 		ndr_desc.res = &pdev->resource[i];
 		ndr_desc.of_node = np;
 		set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);