We have various instances in our HAL where we iterate through some collection of registers, eg:

```rust
for cmd in self.register_block().comd().iter() {
    cmd.reset();
}
```

After updating to the latest `svd2rust` this no longer seems to be possible. I'm unable to iterate at all, and `comd()` expects a `usize`; however, there is no associated constant or anything like I would expect, indicating how many registers are available. Was this change intended, if so why? Do we now need to hard-code values into the HAL which are available in the SVDs but seemingly no longer present in the PACs?