nilfs2: use default_groups in kobj_type

nilfs2: 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 nilfs2 code to use default_groups field which has been
the preferred way since 69dee9413867 ("kobject: Add support for default
attribute groups to kobj_type") so that we can soon get rid of the
obsolete default_attrs field.

Acked-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Link: https://lore.kernel.org/r/20211228144252.390554-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>