sai: HAL implementation for the serial audio interface (only F429 for now).

Some bits are still missing:
- Support for DMA
- Implementation of the new embedded-hal I2S traits
- Documentation about how to set the intermediate SAI clock
- Support for other MCUs

Author: Mathias Gottschlag

src/lib.rs

@@ -117,6 +117,8 @@ pub mod qei;
 pub mod qspi;
 pub mod rcc;
 pub mod rtc;
+#[cfg(feature = "sai")]
+pub mod sai;
 #[cfg(all(feature = "sdio-host", feature = "sdio"))]
 pub mod sdio;
 pub mod serial;