u/file: Improve u_file.cpp a bit

Part-of: <https://gitlab.freedesktop.org/monado/monado/-/merge_requests/2674>

src/xrt/auxiliary/util/u_file.cpp

@@ -1,4 +1,5 @@
 // Copyright 2019-2021, Collabora, Ltd.
+// Copyright 2025, NVIDIA CORPORATION.
 // SPDX-License-Identifier: BSL-1.0
 /*!
  * @file
@@ -28,6 +29,13 @@ namespace fs = std::filesystem;
 namespace fs = std::experimental::filesystem;
 #endif
 
+
+/*
+ *
+ * Helpers
+ *
+ */
+
 static inline fs::path
 get_config_path()
 {
@@ -55,6 +63,13 @@ get_config_path()
 #endif
 }
 
+
+/*
+ *
+ * 'Exported' functions.
+ *
+ */
+
 int
 u_file_get_config_dir(char *out_path, size_t out_path_size)
 {
@@ -105,4 +120,4 @@ u_file_open_file_in_config_dir(const char *filename, const char *mode)
 	return nullptr;
 }
 
-#endif // XRT_OS_LINUX
+#endif // !XRT_OS_LINUX