gfs2: replace ktype default_attrs with default_groups

The kobj_type default_attrs field is being replaced by the
default_groups field. Replace the default_attrs field in gfs2_ktype
with default_groups. Use the ATTRIBUTE_GROUPS macro to create
gfs2_groups.

Signed-off-by: Kimberly Brown <kimbrownkd@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>