doc_rst: rename the media Sphinx suff to Documentation/media

The name of the subsystem is "media", and not "linux_tv". Also,
as we plan to add other stuff there in the future, let's
rename also the media uAPI book to media_uapi, to make it
clearer.

No functional changes.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
diff --git a/Documentation/index.rst b/Documentation/index.rst
index 8bc7bf4..ad07716 100644
--- a/Documentation/index.rst
+++ b/Documentation/index.rst
@@ -14,7 +14,7 @@
    :maxdepth: 2
 
    kernel-documentation
-   linux_tv/index
+   media/media_uapi
 
 Indices and tables
 ==================