nvdimm/pmem: fix creating the dax group

The recent block layer refactoring broke the way how the pmem driver
abused device_add_disk.  Fix this by properly passing the attribute groups
to device_add_disk.

Fixes: 52b85909 ("block: fold register_disk into device_add_disk")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20210922173431.2454024-2-hch@lst.deSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/nvdimm/pmem.c

@@ -380,7 +380,6 @@ static int pmem_attach_disk(struct device *dev,
 	struct nd_pfn_sb *pfn_sb;
 	struct pmem_device *pmem;
 	struct request_queue *q;
-	struct device *gendev;
 	struct gendisk *disk;
 	void *addr;
 	int rc;
@@ -489,10 +488,8 @@ static int pmem_attach_disk(struct device *dev,
 	}
 	dax_write_cache(dax_dev, nvdimm_has_cache(nd_region));
 	pmem->dax_dev = dax_dev;
-	gendev = disk_to_dev(disk);
-	gendev->groups = pmem_attribute_groups;
 
-	device_add_disk(dev, disk, NULL);
+	device_add_disk(dev, disk, pmem_attribute_groups);
 	if (devm_add_action_or_reset(dev, pmem_release_disk, pmem))
 		return -ENOMEM;