Clean up ill-advised or unusual header guards

Cleaned up with scripts/clean-header-guards.pl.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
diff --git a/include/io/task.h b/include/io/task.h
index df9499a..42028cb 100644
--- a/include/io/task.h
+++ b/include/io/task.h
@@ -18,8 +18,8 @@
  *
  */
 
-#ifndef QIO_TASK_H__
-#define QIO_TASK_H__
+#ifndef QIO_TASK_H
+#define QIO_TASK_H
 
 #include "qemu-common.h"
 #include "qom/object.h"
@@ -252,4 +252,4 @@
  */
 Object *qio_task_get_source(QIOTask *task);
 
-#endif /* QIO_TASK_H__ */
+#endif /* QIO_TASK_H */