Update chapter4.md

 fix typo in the fx_directory_information_get() prototype document.

Author: rahmanih

rtos-docs/filex/chapter4.md

@@ -646,7 +646,7 @@ Gets a directory's entry information
 ### Prototype
 
 ```c
-UINT fx_directory_first_full_entry_find(
+UINT fx_directory_information_get(
  FX_MEDIA *media_ptr,
  CHAR *directory_name,
  UINT *attributes,