interface / dap / swd_init() improvements

```
uint8_t swd_init(void)
{
//TODO - DAP_Setup puts GPIO pins in a hi-z state which can
// cause problems on re-init. This needs to be investigated
// and fixed.
DAP_Setup();
PORT_SWD_SETUP();
return 1;
}
```
This function is called several times, during the run, for instance as Target Reset mechanism.. maybe we could use simple flag that marks port already initialized so no need to reinitialize.. or use function that could optionally force port reinitialization? :-)

Start at swd_init(), then inspect DAP_Setup() and PORT_SWD_SETUP() to understand the GPIO high-impedance state during repeated initialization. Reproduce the behavior across target-reset calls and determine whether initialization should be skipped or explicitly forced; done means repeated calls no longer cause the reported re-initialization problems.

Written by the indexing model from the issue text.