Change GPIO inherent methods back to `&self`.

With the embedded-hal rc3 update I changed them to require `&mut self`, but
in retrospect I think `&self` is better, for extra flexibility.

This PR reverts the changes from the rc3 update to inherent methods.

1 files changed, 1 insertions, 1 deletions

diff --git a/examples/rp/src/bin/button.rs b/examples/rp/src/bin/button.rs
index e9054fd48..4ad2ca3b7 100644
--- a/examples/rp/src/bin/button.rs
+++ b/examples/rp/src/bin/button.rs
@@ -16,7 +16,7 @@ async fn main(_spawner: Spawner) {
 
     // Use PIN_28, Pin34 on J0 for RP Pico, as a input.
     // You need to add your own button.
-    let mut button = Input::new(p.PIN_28, Pull::Up);
+    let button = Input::new(p.PIN_28, Pull::Up);
 
     loop {
         if button.is_high() {