package/qt5/qt5base: exclude OpenSSL functionality for Qt 5.6.x

No patch back-porting OpenSSL 1.1.x support to Qt 5.6.x is available.

https://development.qt-project.narkive.com/RW4wxYXY/openssl-1-1-x-support-on-qt-5-6-5-9



Signed-off-by: James Grant <james.grant@jci.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>