ftpd: Remove superfluous defines

These defines are not used and easily conflict with application code.
They are also defined by the standard header file <arpa/ftp.h> if
someone needs them.

cpukit/include/rtems/ftpd.h

@@ -57,15 +57,6 @@ struct rtems_ftpd_configuration
    bool                    verbose;            /* Say hello! */
 };
 
-/*
- * Reply codes.
- */
-#define PRELIM          1       /* positive preliminary */
-#define COMPLETE        2       /* positive completion */
-#define CONTINUE        3       /* positive intermediate */
-#define TRANSIENT       4       /* transient negative completion */
-#define ERROR           5       /* permanent negative completion */
-
 rtems_status_code rtems_ftpd_start(
   const struct rtems_ftpd_configuration *config
 );