vl: add system_wakeup_request tracepoint

It might be useful for tracing migration.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
diff --git a/vl.c b/vl.c
index 41581c1..50693e6 100644
--- a/vl.c
+++ b/vl.c
@@ -1837,6 +1837,8 @@
 
 void qemu_system_wakeup_request(WakeupReason reason)
 {
+    trace_system_wakeup_request(reason);
+
     if (!runstate_check(RUN_STATE_SUSPENDED)) {
         return;
     }