[IA64] Fix VTi domain shutdown

Event channel destruction is now done earlier, this patch does
the corresponding modification in IA64 side. It fixes dom0 crash
when VTI destroyed.

Signed-off-by: Zhang Xin <xing.z.zhang@intel.com>

xen/arch/ia64/vmx/vmx_init.c

@@ -283,9 +283,13 @@ static void vmx_create_event_channels(struct vcpu *v)
 	}
 }
 
+/*
+ * Event channel has destoryed in domain_kill(), so we needn't
+ * do anything here
+ */
 static void vmx_release_assist_channel(struct vcpu *v)
 {
-	free_xen_event_channel(v, v->arch.arch_vmx.xen_port);
+	return;
 }
 
 /*