Some API documentation was missed, rectify that.

Fixes: https://gitlab.com/qemu-project/qemu/-/issues/1497


Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20230315174331.2959-7-alex.bennee@linaro.org>