package/snmppp: requires DES support in openssl

Enable DES in openssl to fix build failure raised since commit
a83d4186

Fixes:
 - http://autobuild.buildroot.org/results/2aece7e503d36ebee2bce526f11b2400b9df761e



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>