fix mc146818rtc wrong subsection name to avoid vmstate_subsection_load() fail

fix mc146818rtc wrong subsection name to avoid vmstate_subsection_load() fail
during incoming migration or loadvm.

Signed-off-by: Zhang Haoyu <zhanghy@sangfor.com.cn>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

hw/timer/mc146818rtc.c

diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c
index 5a107fa..0600c9a 100644
--- a/hw/timer/mc146818rtc.c
+++ b/hw/timer/mc146818rtc.c
@@ -734,7 +734,7 @@
 }
 
 static const VMStateDescription vmstate_rtc_irq_reinject_on_ack_count = {
-    .name = "irq_reinject_on_ack_count",
+    .name = "mc146818rtc/irq_reinject_on_ack_count",
     .version_id = 1,
     .minimum_version_id = 1,
     .fields = (VMStateField[]) {