cargo fix --edition & rustfmt

Or to be precise:
RUST_TARGET_PATH=$(pwd)/targets cargo fix --edition \
--target targets/x86_64-unknown-kernel.json \
--target targets/i686-unknown-kernel.json \
--target targets/aarch64-unknown-kernel.json \
--target targets/riscv64-unknown-kernel.json \
-Zbuild-std=core,alloc --allow-dirty --bin kernel
cargo fmt

src/sync/wait_queue.rs

@@ -31,15 +31,20 @@ impl<T> WaitQueue<T> {
         loop {
             let mut inner = self.inner.lock();
 
-            if let Some(t) = inner.pop_front() {
-                return Ok(t);
-            } else if block {
-                if !self.condition.wait(inner, reason) {
-                    return Err(Error::new(EINTR));
+            match inner.pop_front() {
+                Some(t) => {
+                    return Ok(t);
+                }
+                _ => {
+                    if block {
+                        if !self.condition.wait(inner, reason) {
+                            return Err(Error::new(EINTR));
+                        }
+                        continue;
+                    } else {
+                        return Err(Error::new(EAGAIN));
+                    }
                 }
-                continue;
-            } else {
-                return Err(Error::new(EAGAIN));
             }
         }
     }