package.libopenssl: fix enabling/disabling mdc2

Commit 3dbc86f0 (openssl: bump version, enable mdc2+camellia+tlsext)
form 2010-06-03, forced the build of mdc2. Commit a83d4186
(package/libopenssl: add option to enable some features) added an option
to explicitly disable mdc2, but forgot to amend the existing enabling
option.

It appears that, like most (all?) openssl config options, mdc2 ends up
enabled unless explicitly disabled.

Additionally, mdc2 depends on DES, so without DES, mdc2 gets disabled.

So, drop the explicit enabling option, and make mdc2 select DES.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: "GAUTRON, Erwan" <erwan.gautron@bertin.fr>
Cc: "Weber, Matthew L Collins" <Matthew.Weber@collins.com>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>