MEDIUM: various: Use __ha_barrier_atomic* when relevant.

When protecting data modified by atomic operations, use __ha_barrier_atomic*
to avoid unneeded barriers on x86.
diff --git a/include/common/xref.h b/include/common/xref.h
index a6291f5..48bc07a 100644
--- a/include/common/xref.h
+++ b/include/common/xref.h
@@ -32,7 +32,7 @@
 
 		/* Get the local pointer to the peer. */
 		local = HA_ATOMIC_XCHG(&xref->peer, XREF_BUSY);
-		__ha_barrier_store();
+		__ha_barrier_atomic_store();
 
 		/* If the local pointer is NULL, the peer no longer exists. */
 		if (local == NULL) {