An alternate register access layer (RAL) for i.MX RT MCUs.

Generally, you should prefer [imxrt-ral] over these packages. imxrt-ral provides
a complete register access layer, more than what's available here. imxrt-ral is
also on crates.io. If you're using this, it's because I wrote another experiment
that depends on this experiment.

This RAL

- is more hand written than [imxrt-ral], but not fully hand written!
- has way more packages -- one per IP block -- for uses in drivers and MCUs.
- includes either none or too much higher-level abstractions for using drivers.
- supports a few MCUs that aren't yet available in imxrt-ral.
- doesn't support MCUs that _are_ available in imxrt-ral.
- uses a newer version of [ral-registers].

[imxrt-ral]: https://github.com/imxrt-rs/imxrt-ral
[ral-registers]: https://git.mciantyre.dev/ral-registers

License: APACHE-2.0