xen/panic: use xen_reboot and fix smp_send_stop

Offline vcpu when using stop_self.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index a29693f..25f232b 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -394,6 +394,8 @@
 	load_cr3(swapper_pg_dir);
 	/* should set up a minimal gdt */
 
+	set_cpu_online(cpu, false);
+
 	HYPERVISOR_vcpu_op(VCPUOP_down, cpu, NULL);
 	BUG();
 }