xen/events: replace raw bit ops with functions

In preparation for adding event channel port ops, use set_evtchn()
instead of sync_set_bit().

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 359e983..fec5da4 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -1548,13 +1548,12 @@
 static int retrigger_evtchn(int evtchn)
 {
 	int masked;
-	struct shared_info *s = HYPERVISOR_shared_info;
 
 	if (!VALID_EVTCHN(evtchn))
 		return 0;
 
 	masked = test_and_set_mask(evtchn);
-	sync_set_bit(evtchn, BM(s->evtchn_pending));
+	set_evtchn(evtchn);
 	if (!masked)
 		unmask_evtchn(evtchn);