Implement remaining logic for blocking UART. async is still todo, awaiting DMA

embassy-rp/src/dma.rs

@@ -1,5 +1,7 @@
 use core::sync::atomic::{compiler_fence, Ordering};
 
+use embassy_hal_common::impl_peripheral;
+
 use crate::pac::dma::vals;
 use crate::{pac, peripherals};
 
@@ -35,6 +37,10 @@ impl<T: Channel> Dma<T> {
     }
 }
 
+pub struct NoDma;
+
+impl_peripheral!(NoDma);
+
 mod sealed {
     use super::*;