openssl: disable apps for NOMMU

The openssl binary uses fork() so disable the option and build for !MMU.
Fixes
http://autobuild.buildroot.net/results/45a9b84c16caadbf77b6fc43d7a0001c981a4c87/build-end.log



Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>