Fix doc link

src/common/gpio.rs

@@ -173,7 +173,7 @@ impl<P> Output<P> {
 
     /// Returns `true` if the value of the pad is high.
     ///
-    /// Can differ from `is_set()`, especially in an open drain config.
+    /// Can differ from [`is_set()`](Self::is_set), especially in an open drain config.
     pub fn is_pad_high(&self) -> bool {
         ral::read_reg!(ral::gpio, self.gpio, PSR) & self.mask() != 0
     }