dm sysfs: use default_groups in kobj_type

There are currently 2 ways to create a set of sysfs files for a
kobj_type, through the default_attrs field, and the default_groups
field.  Move the dm sysfs code to use default_groups field which has
been the preferred way since aa30f47c ("kobject: Add support for
default attribute groups to kobj_type") so that we can soon get rid of
the obsolete default_attrs field.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-sysfs.c

@@ -112,6 +112,7 @@ static struct attribute *dm_attrs[] = {
 	&dm_attr_rq_based_seq_io_merge_deadline.attr,
 	NULL,
 };
+ATTRIBUTE_GROUPS(dm);
 
 static const struct sysfs_ops dm_sysfs_ops = {
 	.show	= dm_attr_show,
@@ -120,7 +121,7 @@ static const struct sysfs_ops dm_sysfs_ops = {
 
 static struct kobj_type dm_ktype = {
 	.sysfs_ops	= &dm_sysfs_ops,
-	.default_attrs	= dm_attrs,
+	.default_groups	= dm_groups,
 	.release	= dm_kobject_release,
 };