stm32: Fix vrefbuf trace with log feature

Vrs and Hiz don't implement core::fmt::Display

embassy-stm32/CHANGELOG.md

@@ -8,6 +8,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 <!-- next-header -->
 ## Unreleased - ReleaseDate
 
+- fix: Fix vrefbuf building with log feature
+
 ## 0.3.0 - 2025-08-12
 
 - feat: Added VREFBUF voltage reference buffer driver ([#4524](https://github.com/embassy-rs/embassy/pull/4524))

embassy-stm32/src/vrefbuf/mod.rs

@@ -62,8 +62,8 @@ impl<'d, T: Instance> VoltageReferenceBuffer<'d, T> {
         }
         trace!(
             "Vrefbuf configured with voltage scale {} and impedance mode {}",
-            voltage_scale,
-            impedance_mode
+            voltage_scale as u8,
+            impedance_mode as u8,
         );
         VoltageReferenceBuffer { vrefbuf: PhantomData }
     }