includecheck fix: drivers/xen, evtchn.c

fix the following 'make includecheck' warning:

  drivers/xen/evtchn.c: linux/errno.h is included more than once.
Signed-off-by: NJaswinder Singh Rajput <jaswinderrajput@gmail.com>
Cc:  chrisw@sous-sol.org
Cc: Sam Ravnborg <sam@ravnborg.org>
LKML-Reference: <1247067749.4382.90.camel@ht.satnam>
Acked-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

drivers/xen/evtchn.c

@@ -38,7 +38,6 @@
 #include <linux/string.h>
 #include <linux/errno.h>
 #include <linux/fs.h>
-#include <linux/errno.h>
 #include <linux/miscdevice.h>
 #include <linux/major.h>
 #include <linux/proc_fs.h>