Optimises the buffer passing for nRF SAADC

The buffer will always have been filled and we never explicitly stop the task outside of this code. Thus, we can assume the number of bytes in the slice.

embassy-nrf/src/saadc.rs

@@ -320,7 +320,7 @@ impl<'d, const N: usize> Saadc<'d, N> {
                 r.events_end.reset();
                 r.intenset.write(|w| w.end().set());
 
-                if sampler(&bufs[current_buffer][0..r.result.amount.read().bits() as usize / N])
+                if sampler(&bufs[current_buffer])
                     == SamplerState::Sampled
                 {
                     let next_buffer = 1 - current_buffer;