doc-rst: linux_tv/Makefile: Honor quiet make O=dir

To honor the:

  make O=dir [targets] Locate all output files in "dir"

* activate kernel-include directive
* export BUILDDIR=$(BUILDDIR)
* linux_tv: replace '.. include::' with '.. kernel-include:: $BUILDDIR/<foo.h.rst>'

Signed-off-by: Markus Heiser <markus.heiser@darmarIT.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
diff --git a/Documentation/conf.py b/Documentation/conf.py
index f35748b..224240b5 100644
--- a/Documentation/conf.py
+++ b/Documentation/conf.py
@@ -28,7 +28,7 @@
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
-extensions = ['kernel-doc', 'rstFlatTable']
+extensions = ['kernel-doc', 'rstFlatTable', 'kernel_include']
 
 # Gracefully handle missing rst2pdf.
 try: