staging/lustre: fix build error

We missed one file...
Signed-off-by: Peng Tao <tao.peng@emc.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/obdclass/Makefile

@@ -7,7 +7,7 @@ obdclass-y := linux/linux-module.o linux/linux-obdo.o linux/linux-sysctl.o \
 	      local_storage.o statfs_pack.o obdo.o obd_config.o obd_mount.o\
 	      mea.o lu_object.o dt_object.o capa.o cl_object.o   \
 	      cl_page.o cl_lock.o cl_io.o lu_ref.o acl.o idmap.o	   \
-	      md_local_object.o
+	      md_local_object.o lu_ucred.o
 
 
 ccflags-y := -I$(src)/../include