libnvdimm: fix namespace seed creation

A new BLK namespace "seed" device is created whenever the current seed
is successfully probed.  However, if that namespace is assigned to a BTT
it may never directly experience a successful probe as it is a
subordinate device to a BTT configuration.

The effect of the current code is that no new namespaces can be
instantiated, after the seed namespace, to consume available BLK DPA
capacity.  Fix this by treating a successful BTT probe event as a
successful probe event for the backing namespace.
Reported-by: NNicholas Moulin <nicholas.w.moulin@linux.intel.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

drivers/nvdimm/region_devs.c

@@ -458,10 +458,15 @@ static void nd_region_notify_driver_action(struct nvdimm_bus *nvdimm_bus,
 		nvdimm_bus_unlock(dev);
 	}
 	if (is_nd_btt(dev) && probe) {
+		struct nd_btt *nd_btt = to_nd_btt(dev);
+
 		nd_region = to_nd_region(dev->parent);
 		nvdimm_bus_lock(dev);
 		if (nd_region->btt_seed == dev)
 			nd_region_create_btt_seed(nd_region);
+		if (nd_region->ns_seed == &nd_btt->ndns->dev &&
+				is_nd_blk(dev->parent))
+			nd_region_create_blk_seed(nd_region);
 		nvdimm_bus_unlock(dev);
 	}
 }