sandbox: Fix comment for os_open()

This has the wrong #define in the function comment. Fix it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Marek Vasut <marex@denx.de>
diff --git a/include/os.h b/include/os.h
index e3645e0..a758f09 100644
--- a/include/os.h
+++ b/include/os.h
@@ -64,7 +64,7 @@
  * Access to the OS open() system call
  *
  * \param pathname	Pathname of file to open
- * \param flags		Flags, like O_RDONLY, O_RDWR
+ * \param flags		Flags, like OS_O_RDONLY, OS_O_RDWR
  * \return file descriptor, or -1 on error
  */
 int os_open(const char *pathname, int flags);