Documentation: man-page for command bootd

Provide a man-page for the bootd command.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/usage/index.rst b/doc/usage/index.rst
index f7f03ae..815b032 100644
--- a/doc/usage/index.rst
+++ b/doc/usage/index.rst
@@ -23,6 +23,7 @@
    cmd/addrmap
    cmd/askenv
    cmd/base
+   cmd/bootd
    cmd/bootdev
    cmd/bootefi
    cmd/bootflow