windows: Rename header guard

Change-Id: I1edd5dbea5850e0bba65df0bed232ca1fcf8505e
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/windows.h b/windows.h
index 468fd12..517e3f8 100644
--- a/windows.h
+++ b/windows.h
@@ -1,8 +1,8 @@
 /* SPDX-License-Identifier: Apache-2.0 */
 /* Copyright (C) 2018 IBM Corp. */
 
-#ifndef MBOXD_WINDOWS_H
-#define MBOXD_WINDOWS_H
+#ifndef WINDOWS_H
+#define WINDOWS_H
 
 #define NO_FLUSH	false
 #define WITH_FLUSH	true
@@ -33,4 +33,4 @@
 		      struct window_context **this_window,
 		      uint32_t offset, bool exact);
 
-#endif /* MBOXD_WINDOWS_H */
+#endif /* WINDOWS_H */