file-system session: use same dirent size as VFS

This change allows for the conversion of directory entries in place
(i.e., in the VFS server) and anticipates the potential future merge of
both types into one.

Issue #3547

repos/os/include/file_system_session/file_system_session.h

@@ -116,7 +116,7 @@ namespace File_system {
 	 */
 	enum Mode { STAT_ONLY = 0, READ_ONLY = 1, WRITE_ONLY = 2, READ_WRITE = 3 };
 
-	enum { MAX_NAME_LEN = 256, MAX_PATH_LEN = 1024 };
+	enum { MAX_NAME_LEN = 128, MAX_PATH_LEN = 1024 };
 
 	/**
 	 * File offset constant for reading or writing to the end of a file