xen: move events.c to drivers/xen for IA64/Xen support

move arch/x86/xen/events.c undedr drivers/xen to share codes
with x86 and ia64. And minor adjustment to compile.
ia64/xen also uses events.c

Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
new file mode 100644
index 0000000..10ddfe0
--- /dev/null
+++ b/include/xen/xen-ops.h
@@ -0,0 +1,8 @@
+#ifndef INCLUDE_XEN_OPS_H
+#define INCLUDE_XEN_OPS_H
+
+#include <linux/percpu.h>
+
+DECLARE_PER_CPU(struct vcpu_info *, xen_vcpu);
+
+#endif /* INCLUDE_XEN_OPS_H */