Adjust pin-names to FooPin.

Move common bits up to spi/mod.rs.
Isolate the RNG interrupt in a sub-module to avoid conflict with the const.

embassy-stm32/src/time.rs

@@ -1,4 +1,3 @@
-
 //! Time units
 
 /// Bits per second
@@ -124,4 +123,4 @@ impl Into<MicroSeconds> for MilliSeconds {
     fn into(self) -> MicroSeconds {
         MicroSeconds(self.0 * 1_000)
     }
-}
+}