stm32: add rust stable support

embassy-stm32/src/exti.rs

@@ -150,7 +150,6 @@ mod eh02 {
 mod eh1 {
     use super::*;
     use core::convert::Infallible;
-    use futures::FutureExt;
 
     impl<'d, T: GpioPin> embedded_hal_1::digital::ErrorType for ExtiInput<'d, T> {
         type Error = Infallible;
@@ -165,6 +164,11 @@ mod eh1 {
             Ok(self.is_low())
         }
     }
+}
+#[cfg(all(feature = "unstable-traits", feature = "nightly"))]
+mod eh1a {
+    use super::*;
+    use futures::FutureExt;
 
     impl<'d, T: GpioPin> embedded_hal_async::digital::Wait for ExtiInput<'d, T> {
         type WaitForHighFuture<'a>