xen: remove xen/evtchn.h

Impact: cleanup

It's a usermode header for users of /dev/xen/evtchn.
Signed-off-by: NJeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: NIan Campbell <ian.campbell@citrix.com>
[corresponds to b60e48cec12f in git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git]
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/xenbus/xenbus_probe_backend.c

@@ -48,7 +48,6 @@
 #include <asm/xen/hypervisor.h>
 #include <asm/hypervisor.h>
 #include <xen/xenbus.h>
-#include <xen/evtchn.h>
 #include <xen/features.h>
 
 #include "xenbus_comms.h"