savevm: fix wrong initialization by ram_control_load_hook

It should set negative error value rather than 0 in QEMUFile
if there has been an error.

Reviewed-by: Michael R. Hines <mrhines@us.ibm.com>
Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

savevm.c

diff --git a/savevm.c b/savevm.c
index a834c6f..2f631d4 100644
--- a/savevm.c
+++ b/savevm.c
@@ -649,7 +649,7 @@
 
 void ram_control_load_hook(QEMUFile *f, uint64_t flags)
 {
-    int ret = 0;
+    int ret = -EINVAL;
 
     if (f->ops->hook_ram_load) {
         ret = f->ops->hook_ram_load(f, f->opaque, flags);