For LTE tdd_ul_dl_config is

    enum [
         "[Configuration 2] 5ms 2UL 6DL (default)",
         "[Configuration 6] 5ms 5UL 3DL (maximum uplink)"
    ],

but default was outside of that enum. The code in enb.jinja2.cfg actually uses
the first option from the enum as the default.

-> Fix default in schema.

tdd_ul_dl_config in NR seems to be already correct.