[PATCH] docs: device-mapper: Add dm-clone to documentation index

[Geert Uytterhoeven <geert+renesas@xxxxxxxxx>]

When the dm-clone documentation was added, it was not added to the
documentation index, leading to a warning when building the
documentation:

    Documentation/admin-guide/device-mapper/dm-clone.rst: WARNING: document isn't included in any toctree

Fixes: 7431b7835f554f86 ("dm: add clone target")
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
---
 Documentation/admin-guide/device-mapper/index.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/admin-guide/device-mapper/index.rst b/Documentation/admin-guide/device-mapper/index.rst
index 4872fb6d29524593..ec62fcc8eeceed83 100644
--- a/Documentation/admin-guide/device-mapper/index.rst
+++ b/Documentation/admin-guide/device-mapper/index.rst
@@ -8,6 +8,7 @@ Device Mapper
     cache-policies
     cache
     delay
+    dm-clone
     dm-crypt
     dm-dust
     dm-flakey