Recently bpf docs were converted to RST format.  The new files were not
added to the top level toctree.  This causes build system to emit a
warning of type

	WARNING: document isn't included in any toctree

Add bpf/index.rst to Documentation/index.rst

Signed-off-by: Tobin C. Harding <redacted>
---
 Documentation/index.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/index.rst b/Documentation/index.rst
index 5d310d960f82..24339a9c2ef8 100644
--- a/Documentation/index.rst
+++ b/Documentation/index.rst

@@ -92,6 +92,7 @@ needed).
    crypto/index
    filesystems/index
    vm/index
+   bpf/index
 
 Architecture-specific documentation
 -----------------------------------

-- 
2.17.1