Vivado: simplify programming TCL script
Vivado: simplify programming TCL script

The previously used template was unnecessarily complex. We anyhow only
support the standard case of a single board being connected to the local
machine, and in this case, the default set of TCL commands works just
fine (and also gives an appropriate error if the board is not found, for
example).

olofk/fusesoc,lowRISC/fusesoc,lowRISC/fusesoc,olofk/fusesoc