OpenOCD config file updates

[josuah]

As discussed in #513 here are two commits adjusting the config:

• 63adcb9 which fixes a bug when $_CHIPNAME is not defined:
  set _CHIPNAME ecp5 as the only change.

• 95b6fa1 which convert the syntax to the supported format.

These kind of refactoring are not expected to break anything, but still has the risk of any refactoring.
Should I keep the second commit away until everything can be tested again?

[enjoy-digital]

Thanks @josuah, we are still using an old version of OpenOCD (https://github.com/enjoy-digital/openocd) and we'll have to switch to upstream before merging (at least test it on my side and evaluate the changes required for some other projects). I'll try to do it in not too long, but probably not before the end of the month.

[josuah]

I am actually glad that this gets deferred as it means it costs not more than it helps.
I will be so very patient... :)

[josuah]

Big refactors are best done by the authors themselves, that way no pressure either direction :)