staging: sw_sync: sw_sync_timeline_ops can be static

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Changlong Xie <changlongx.xie@intel.com>
Acked-by: Erik Gilling <konkers@android.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>