windows: Add WINDOWS prefix to FLUSH macros

Change-Id: Id1a7890259ce95bfbbce55c6e76218bd85d68d86
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/windows.h b/windows.h
index 517e3f8..c541c22 100644
--- a/windows.h
+++ b/windows.h
@@ -4,8 +4,8 @@
 #ifndef WINDOWS_H
 #define WINDOWS_H
 
-#define NO_FLUSH	false
-#define WITH_FLUSH	true
+#define WINDOWS_NO_FLUSH	false
+#define WINDOWS_WITH_FLUSH	true
 
 #include "mbox.h"