uefi: workaround dead code warning on nightly

This is a more fine-grained approach than taken in
716f9bc.

Author: phip1611

uefi/src/proto/mod.rs

@@ -9,6 +9,8 @@
 //!
 //! [`BootServices`]: crate::table::boot::BootServices#accessing-protocols
 
+#![warn(dead_code)] // https://github.com/rust-osdev/uefi-rs/issues/1205
+
 use crate::Identify;
 use core::ffi::c_void;