xen: Add Xen hypercall for sleep state in the cmos_s3 callback.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/xen-stub.c b/xen-stub.c
index 8d2fa54..a4f35a1 100644
--- a/xen-stub.c
+++ b/xen-stub.c
@@ -22,6 +22,10 @@
 {
 }
 
+void xen_cmos_set_s3_resume(void *opaque, int irq, int level)
+{
+}
+
 void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size)
 {
 }