hw/xen: Add xenstore operations to allow redirection to internal emulation

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
diff --git a/softmmu/globals.c b/softmmu/globals.c
index dda3298..39678aa 100644
--- a/softmmu/globals.c
+++ b/softmmu/globals.c
@@ -68,3 +68,4 @@
 struct evtchn_backend_ops *xen_evtchn_ops;
 struct gnttab_backend_ops *xen_gnttab_ops;
 struct foreignmem_backend_ops *xen_foreignmem_ops;
+struct xenstore_backend_ops *xen_xenstore_ops;