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/Makefile.sphinx b/Documentation/Makefile.sphinx
index 6a093e4..5aa2161 100644
--- a/Documentation/Makefile.sphinx
+++ b/Documentation/Makefile.sphinx
@@ -32,10 +32,10 @@
 I18NSPHINXOPTS  = $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) .
 
 quiet_cmd_sphinx = SPHINX  $@
-      cmd_sphinx = $(SPHINXBUILD) -b $2 $(ALLSPHINXOPTS) $(BUILDDIR)/$2
+      cmd_sphinx = BUILDDIR=$(BUILDDIR) $(SPHINXBUILD) -b $2 $(ALLSPHINXOPTS) $(BUILDDIR)/$2
 
 htmldocs:
-	$(MAKE) BUILDDIR=$(objtree)/$(BUILDDIR) -f $(srctree)/Documentation/linux_tv/Makefile $@
+	$(MAKE) BUILDDIR=$(BUILDDIR) -f $(srctree)/Documentation/linux_tv/Makefile $@
 	$(call cmd,sphinx,html)
 
 pdfdocs: