xen: Add proper irq accounting for HYPERCALL vector

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Xen <xen-devel@lists.xenproject.org>
Link: http://lkml.kernel.org/r/20140223212738.808648133@linutronix.deSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/xen/events/events_base.c

@@ -1235,6 +1235,7 @@ void xen_evtchn_do_upcall(struct pt_regs *regs)
 #ifdef CONFIG_X86
 	exit_idle();
 #endif
+	inc_irq_stat(irq_hv_callback_count);
 
 	__xen_evtchn_do_upcall();