x86: paravirt spinlocks, modular build fix

fix:

  MODPOST 408 modules
ERROR: "pv_lock_ops" [net/dccp/dccp.ko] undefined!
ERROR: "pv_lock_ops" [fs/jbd2/jbd2.ko] undefined!
ERROR: "pv_lock_ops" [drivers/media/common/saa7146_vv.ko] undefined!

Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/paravirt.c

@@ -472,6 +472,7 @@ struct pv_lock_ops pv_lock_ops = {
 	.spin_unlock = __ticket_spin_unlock,
 #endif
 };
+EXPORT_SYMBOL_GPL(pv_lock_ops);
 
 EXPORT_SYMBOL_GPL(pv_time_ops);
 EXPORT_SYMBOL    (pv_cpu_ops);