Merge #1049

1049: embassy-nrf: Add I2S module r=lulf a=chris-zen

This PR adds I2S support for the nrf52 series (`nrf52832`, `nrf52833`, `nrf52840`).

We could only test it in a `nrf52840` in master mode for an output stream (see `i2s_waveform` example), using a clone of the [Adafruit I2S Stereo Decoder - UDA1334A](https://learn.adafruit.com/adafruit-i2s-stereo-decoder-uda1334a/overview).

We were wondering if this could be a welcome addition to embassy, as we are working on this very informally and don't have much free time for it.

<img src="https://user-images.githubusercontent.com/932644/202316127-a8cf90ef-1e1a-4e1d-b796-961b8ad6cef5.png" width="600">

https://user-images.githubusercontent.com/932644/202316609-e53cd912-e463-4e01-839e-0bbdf37020da.mp4


Co-authored-by: `@brainstorm` <brainstorm@nopcode.org>

Co-authored-by: Christian Perez Llamas <932644+chris-zen@users.noreply.github.com>
Co-authored-by: Roman Valls Guimera <brainstorm@users.noreply.github.com>

embassy-nrf/src/lib.rs

@@ -78,6 +78,8 @@ pub mod buffered_uarte;
 pub mod gpio;
 #[cfg(feature = "gpiote")]
 pub mod gpiote;
+#[cfg(any(feature = "nrf52832", feature = "nrf52833", feature = "nrf52840"))]
+pub mod i2s;
 #[cfg(not(any(feature = "_nrf5340", feature = "_nrf9160")))]
 pub mod nvmc;
 #[cfg(any(