QXL: fix reloading of vram64 attribute

Commit b4a5fd95 introduced vram64 attribute for QXL video device but
there were two issues.  Only function
qemuMonitorJSONUpdateVideoVram64Size should update the vram64 attribute
and also the value is in MiB, not in B.
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>

src/qemu/qemu_monitor_json.c

@@ -1483,17 +1483,6 @@ qemuMonitorJSONUpdateVideoMemorySize(qemuMonitorPtr mon,
         }
         video->vram = prop.val.ul / 1024;
 
-        if (video->vram64 != 0) {
-            if (qemuMonitorJSONGetObjectProperty(mon, path,
-                                                 "vram64_size_mb", &prop) < 0) {
-                virReportError(VIR_ERR_INTERNAL_ERROR,
-                               _("QOM Object '%s' has no property 'vram64_size_mb'"),
-                               path);
-                return -1;
-            }
-            video->vram64 = prop.val.ul / 1024;
-        }
-
         if (qemuMonitorJSONGetObjectProperty(mon, path, "ram_size", &prop) < 0) {
             virReportError(VIR_ERR_INTERNAL_ERROR,
                            _("QOM Object '%s' has no property 'ram_size'"),
@@ -1555,7 +1544,7 @@ qemuMonitorJSONUpdateVideoVram64Size(qemuMonitorPtr mon,
                                path);
                 return -1;
             }
-            video->vram64 = prop.val.ul / 1024;
+            video->vram64 = prop.val.ul * 1024;
         }
         break;
     case VIR_DOMAIN_VIDEO_TYPE_VGA: