libceph: make DEFINE_RB_* helpers more general

Initially for ceph_pg_mapping, ceph_spg_mapping and ceph_hobject_id,
compared with ceph_pg_compare(), ceph_spg_compare() and hoid_compare()
respectively.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
1 file changed