5045 use atomic_{inc,dec}_* instead of atomic_add_*

@@ -177,11 +177,11 @@
          */
         vfsp->vfs_bsize = DEV_BSIZE;
         vfsp->vfs_fstype = objfs_fstype;
         do {
                 dev = makedevice(objfs_major,
-                    atomic_add_32_nv(&objfs_minor, 1) & L_MAXMIN32);
+                    atomic_inc_32_nv(&objfs_minor) & L_MAXMIN32);
         } while (vfs_devismounted(dev));
         vfs_make_fsid(&vfsp->vfs_fsid, dev, objfs_fstype);
         vfsp->vfs_data = data;
         vfsp->vfs_dev = dev;