doc: remove licensing for moved ext/ components

ext/fs/fat and ext/hal/nordic were moved out of the ext folder and into
external modules so we should remove the licensing exceptions noted in
this document.

kconfig and kbuild were removed from the zephyr repo too.

Signed-off-by: David B. Kinder <david.b.kinder@intel.com>
diff --git a/doc/LICENSING.rst b/doc/LICENSING.rst
index 84c5652..330d75c 100644
--- a/doc/LICENSING.rst
+++ b/doc/LICENSING.rst
@@ -16,36 +16,11 @@
 .. _GPLv2 License:
    https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/COPYING
 
-*kconfig* and *kbuild*
-  *Origin:* Linux Kernel
-
-  *Licensing:* `GPLv2 License`_
-
 *scripts/{checkpatch.pl,checkstack.pl,get_maintainers.pl,spelling.txt}*
   *Origin:* Linux Kernel
 
   *Licensing:* `GPLv2 License`_
 
-*ext/fs/fat/*
-  *Origin:* FatFs is a file system based on the FAT file system specification.  This is
-  provided by ELM Chan http://elm-chan.org/fsw/ff/00index_e.html
-
-  *Licensing*:
-
-    Copyright (C) 2016, ChaN, all right reserved.
-
-    FatFs module is an open source software. Redistribution and use of FatFs in
-    source and binary forms, with or without modification, are permitted provided
-    that the following condition is met:
-
-    1. Redistributions of source code must retain the above copyright notice,
-       this condition and the following disclaimer.
-
-    This software is provided by the copyright holder and contributors "AS IS"
-    and any warranties related to this software are DISCLAIMED.
-    The copyright owner or contributors be NOT LIABLE for any damages caused
-    by use of this software.
-
 *ext/hal/cmsis/*
   *Origin:* https://github.com/ARM-software/CMSIS_5.git
 
@@ -53,12 +28,3 @@
 
 .. _ext/hal/cmsis source:
    https://github.com/zephyrproject-rtos/zephyr/blob/master/ext/hal/cmsis/Include/cmsis_version.h
-
-*ext/hal/nordic/*
-  *Origin:* https://github.com/NordicSemiconductor/nrfx.git
-
-  *Licensing*: 3-clause BSD (see `ext/hal/nordic source`_)
-
-.. _ext/hal/nordic source:
-   https://github.com/zephyrproject-rtos/zephyr/blob/master/ext/hal/nordic/nrfx/nrfx.h
-