advice: add enum variants for missing advice variables

advice: add enum variants for missing advice variables

In daef1b300b0 (Merge branch 'hw/advice-add-nothing', 2020-02-14), two
advice settings were introduced into the `advice_config` array.

Subsequently, c4a09cc9ccb (Merge branch 'hw/advise-ng', 2020-03-25)
started to deprecate `advice_config` in favor of a new array,
`advice_setting`.

However, the latter branch did not include the former branch, and
therefore `advice_setting` is missing the two entries added by the
`hw/advice-add-nothing` branch.

These are currently the only entries in `advice_config` missing from
`advice_setting`.

Signed-off-by: Ben Boeckel <mathstuf@gmail.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>