stm32: Allow for RccPeripheral without reset field

This fix build on F0, since it doesn't have DMARST. This change makes
RccPeripheral::reset a no-op on peripherals where a reset field couldn't
be found

embassy-stm32/src/bdma/mod.rs

@@ -177,7 +177,7 @@ pub(crate) unsafe fn init() {
     }
     pac::peripherals! {
         (bdma, $peri:ident) => {
-            crate::peripherals::$peri::enable();
+            <crate::peripherals::$peri as RccPeripheral>::enable();
         };
     }
 }

embassy-stm32/src/rcc/mod.rs

@@ -121,6 +121,35 @@ crate::pac::peripheral_rcc!(
             }
         }
 
+        impl RccPeripheral for peripherals::$inst {}
+    };
+    ($inst:ident, $clk:ident, $enable:ident, $perien:ident) => {
+        impl sealed::RccPeripheral for peripherals::$inst {
+            fn frequency() -> crate::time::Hertz {
+                critical_section::with(|_| {
+                    unsafe {
+                        let freqs = get_freqs();
+                        freqs.$clk
+                    }
+                })
+            }
+            fn enable() {
+                critical_section::with(|_| {
+                    unsafe {
+                        crate::pac::RCC.$enable().modify(|w| w.$perien(true));
+                    }
+                })
+            }
+            fn disable() {
+                critical_section::with(|_| {
+                    unsafe {
+                        crate::pac::RCC.$enable().modify(|w| w.$perien(false));
+                    }
+                })
+            }
+            fn reset() {}
+        }
+
         impl RccPeripheral for peripherals::$inst {}
     };
 );