Fix warnings in recent nightly.

embassy-nrf/src/gpio.rs

@@ -473,10 +473,12 @@ impl sealed::Pin for AnyPin {
 
 // ====================
 
+#[cfg(not(feature = "_nrf51"))]
 pub(crate) trait PselBits {
     fn psel_bits(&self) -> u32;
 }
 
+#[cfg(not(feature = "_nrf51"))]
 impl<'a, P: Pin> PselBits for Option<PeripheralRef<'a, P>> {
     #[inline]
     fn psel_bits(&self) -> u32 {

embassy-nrf/src/gpiote.rs

@@ -167,8 +167,10 @@ unsafe fn handle_gpiote_interrupt() {
     }
 }
 
+#[cfg(not(feature = "_nrf51"))]
 struct BitIter(u32);
 
+#[cfg(not(feature = "_nrf51"))]
 impl Iterator for BitIter {
     type Item = u32;
 

embassy-nrf/src/timer.rs

@@ -21,8 +21,6 @@ pub(crate) mod sealed {
         fn regs() -> &'static pac::timer0::RegisterBlock;
     }
     pub trait ExtendedInstance {}
-
-    pub trait TimerType {}
 }
 
 /// Basic Timer instance.