CHIRP

- the device does include a `tune_step` field in it's channel memory block, but
- `get_features()` sets `has_tuning_step = False` and the `tune_step` field is never modified.
- Code trying to set channels examines `has_nostep_tuning` when deciding to emit an error

```
if self.valid_tuning_steps and not self.has_nostep_tuning:
try:
step = required_step(mem.freq)
if step not in self.valid_tuning_steps:
msg = ValidationError("Frequency requires %.2fkHz step" %
required_step(mem.freq))
msgs.append(msg)
except errors.InvalidDataError, e:
msgs.append(str(e))

```

- setting `has_nostep_tuning` works, but note that `valid_tuning_steps` is set to `[5.0, 10.0, 15.0, 20.0, 25.0, 30.0, 50.0, 100.0]` (aka `COMMON_TUNING_STEPS`), which doesn't match the settable tuning steps on the radio, which are: `[2.5, 5.0, 6.25, 10.0, 12.5, 20, 25, 30, 50]`