Fix the following documentation build error, which was introduced when
Documentation/arch/powerpc/htm.rst was added to the repository without
any reference to the document.

Documentation/arch/powerpc/htm.rst: WARNING: document isn't included in any toctree [toc.not_included]

Fixes: ab1456c5aa7a ("powerpc/pseries/htmdump: Add documentation for H_HTM debugfs interface")
Acked-by: Randy Dunlap <redacted>
Tested-by: Randy Dunlap <redacted>
Signed-off-by: Brigham Campbell <redacted>
---
Changes in v3:
 - Edit commit message to conform better to de facto kernel development style.
 - No changes to the diff.

 Documentation/arch/powerpc/index.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/arch/powerpc/index.rst b/Documentation/arch/powerpc/index.rst
index 0560cbae5fa1..53fc9f89f3e4 100644
--- a/Documentation/arch/powerpc/index.rst
+++ b/Documentation/arch/powerpc/index.rst

@@ -19,6 +19,7 @@ powerpc
     elf_hwcaps
     elfnote
     firmware-assisted-dump
+    htm
     hvcs