Re-adds embassy macros for stm32

* Hook RCC config into chip config and use chip-specific RCC init
  function
* RTC/clock setup is ignored for now

embassy-stm32/src/rcc/h7/mod.rs

@@ -527,3 +527,7 @@ impl<'d> Rcc<'d> {
         }
     }
 }
+
+pub unsafe fn init(config: Config) {
+    // TODO
+}