Cleans up some clippy lints

src/iface/interface.rs

@@ -1015,22 +1015,14 @@ impl<'a> Interface<'a> {
         self.inner.now = timestamp;
 
         #[cfg(feature = "proto-ipv4-fragmentation")]
-        if let Err(e) = self
-            .fragments
+        self.fragments
             .ipv4_fragments
-            .remove_when(|frag| Ok(timestamp >= frag.expires_at()?))
-        {
-            return Err(e);
-        }
+            .remove_when(|frag| Ok(timestamp >= frag.expires_at()?))?;
 
         #[cfg(feature = "proto-sixlowpan-fragmentation")]
-        if let Err(e) = self
-            .fragments
+        self.fragments
             .sixlowpan_fragments
-            .remove_when(|frag| Ok(timestamp >= frag.expires_at()?))
-        {
-            return Err(e);
-        }
+            .remove_when(|frag| Ok(timestamp >= frag.expires_at()?))?;
 
         #[cfg(feature = "proto-ipv4-fragmentation")]
         match self.ipv4_egress(device) {

src/wire/dhcpv4.rs

@@ -364,7 +364,7 @@ impl<T: AsRef<[u8]>> Packet<T> {
         let mut buf = &self.buffer.as_ref()[field::OPTIONS];
         iter::from_fn(move || {
             loop {
-                match buf.get(0).copied() {
+                match buf.first().copied() {
                     // No more options, return.
                     None => return None,
                     Some(field::OPT_END) => return None,