Fix most Clippy warnings.

third_party/lang-items/src/allocator.rs

@@ -44,6 +44,7 @@ impl TockAllocator {
 }
 
 unsafe impl GlobalAlloc for TockAllocator {
+    #[allow(clippy::let_and_return)]
     unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
         let ptr = HEAP
             .allocate_first_fit(layout)

third_party/libtock-drivers/src/console.rs

@@ -25,6 +25,7 @@ pub struct Console {
 }
 
 impl Console {
+    #[allow(clippy::new_without_default)]
     pub fn new() -> Console {
         Console {
             allow_buffer: [0; BUFFER_SIZE],

third_party/libtock-drivers/src/rng.rs

@@ -41,5 +41,5 @@ pub fn fill_buffer(buf: &mut [u8]) -> bool {
     }
 
     util::yieldk_for(|| is_filled.get());
-    return true;
+    true
 }

third_party/libtock-drivers/src/usb_ctap_hid.rs

@@ -173,6 +173,7 @@ pub fn send_or_recv(buf: &mut [u8; 64]) -> SendOrRecvStatus {
 
 // Same as recv, but with a timeout.
 // If the timeout elapses, return None.
+#[allow(clippy::let_and_return)]
 pub fn recv_with_timeout(
     buf: &mut [u8; 64],
     timeout_delay: Duration<isize>,
@@ -199,6 +200,7 @@ pub fn recv_with_timeout(
 
 // Same as send_or_recv, but with a timeout.
 // If the timeout elapses, return None.
+#[allow(clippy::let_and_return)]
 pub fn send_or_recv_with_timeout(
     buf: &mut [u8; 64],
     timeout_delay: Duration<isize>,