Update loopback.rs

src/phy/loopback.rs

@@ -1,12 +1,7 @@
-#[cfg(feature = "std")]
-use std::vec::Vec;
-#[cfg(feature = "std")]
-use std::collections::VecDeque;
-#[cfg(feature = "alloc")]
 use alloc::vec::Vec;
-#[cfg(all(feature = "alloc", not(feature = "rust-1_28")))]
+#[cfg(not(feature = "rust-1_28"))]
 use alloc::collections::VecDeque;
-#[cfg(all(feature = "alloc", feature = "rust-1_28"))]
+#[cfg(feature = "rust-1_28")]
 use alloc::VecDeque;
 
 use crate::Result;