vmstate: check subsection_found is enough

subsection_found is true implies vmdesc is not NULL.

This patch remove the additional check on vmdesc and rename
subsection_found to vmdesc_has_subsections to make it more self-explain.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>

Message-Id: <20190403011016.12549-1-richardw.yang@linux.intel.com>
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

migration/vmstate.c

@@ -496,7 +496,7 @@ static int vmstate_subsection_save(QEMUFile *f, const VMStateDescription *vmsd,
                                    void *opaque, QJSON *vmdesc)
 {
     const VMStateDescription **sub = vmsd->subsections;
-    bool subsection_found = false;
+    bool vmdesc_has_subsections = false;
     int ret = 0;
 
     trace_vmstate_subsection_save_top(vmsd->name);
@@ -508,9 +508,9 @@ static int vmstate_subsection_save(QEMUFile *f, const VMStateDescription *vmsd,
             trace_vmstate_subsection_save_loop(vmsd->name, vmsdsub->name);
             if (vmdesc) {
                 /* Only create subsection array when we have any */
-                if (!subsection_found) {
+                if (!vmdesc_has_subsections) {
                     json_start_array(vmdesc, "subsections");
-                    subsection_found = true;
+                    vmdesc_has_subsections = true;
                 }
 
                 json_start_object(vmdesc, NULL);
@@ -533,7 +533,7 @@ static int vmstate_subsection_save(QEMUFile *f, const VMStateDescription *vmsd,
         sub++;
     }
 
-    if (vmdesc && subsection_found) {
+    if (vmdesc_has_subsections) {
         json_end_array(vmdesc);
     }