xen: remove unused global, xen_xcg

Reviewed-by: NStefan Weil <sw@weilnetz.de>
Signed-off-by: NJim Meyering <meyering@redhat.com>
Acked-by: NStefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

hw/xen/xen_backend.c

@@ -45,7 +45,6 @@
 
 /* public */
 XenXC xen_xc = XC_HANDLER_INITIAL_VALUE;
-XenGnttab xen_xcg = XC_HANDLER_INITIAL_VALUE;
 struct xs_handle *xenstore = NULL;
 const char *xen_protocol;