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

@@ -166,6 +166,18 @@ pub mod pwm;
 pub mod qei;
 #[cfg(feature = "device-selected")]
 pub mod rcc;
+#[cfg(any(
+    feature = "stm32f413",
+    feature = "stm32f423",
+    feature = "stm32f427",
+    feature = "stm32f429",
+    feature = "stm32f437",
+    feature = "stm32f439",
+    feature = "stm32f446",
+    feature = "stm32f469",
+    feature = "stm32f469",
+))]
+pub mod sai;
 #[cfg(all(
     feature = "sdio",
     not(any(feature = "stm32f410", feature = "stm32f446",))