nvdimm/pmem: fix creating the dax group

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: 6ccb127dbc90 ("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.de
Signed-off-by: Dan Williams <dan.j.williams@intel.com>