rust: allow dead_code for never constructed bindings

Starting with the upcoming Rust 1.80.0 (since upstream commit 35130d7233e9
("Detect pub structs never constructed and unused associated constants
in traits")), the `dead_code` pass detects more cases, which triggers
in the `bindings` crate:

    warning: struct `boot_params` is never constructed
        --> rust/bindings/bindings_generated.rs:10684:12
        |
    10684 | pub struct boot_params {
        |            ^^^^^^^^^^^
        |
        = note: `#[warn(dead_code)]` on by default

As well as in the `uapi` one:

    warning: struct `boot_params` is never constructed
        --> rust/uapi/uapi_generated.rs:10392:12
        |
    10392 | pub struct boot_params {
        |            ^^^^^^^^^^^
        |
        = note: `#[warn(dead_code)]` on by default

These are all expected, since we do not use all the structs in the
bindings that `bindgen` generates from the C headers.

Therefore, allow them.

Reviewed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Reviewed-by: Finn Behrens <me@kloenk.dev>
Tested-by: Benno Lossin <benno.lossin@proton.me>
Tested-by: Andreas Hindborg <a.hindborg@samsung.com>
Link: https://lore.kernel.org/r/20240709160615.998336-4-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

rust/bindings/lib.rs

@@ -24,6 +24,7 @@
     unsafe_op_in_unsafe_fn
 )]
 
+#[allow(dead_code)]
 mod bindings_raw {
     // Use glob import here to expose all helpers.
     // Symbols defined within the module will take precedence to the glob import.

rust/uapi/lib.rs

@@ -14,6 +14,7 @@
 #![cfg_attr(test, allow(unsafe_op_in_unsafe_fn))]
 #![allow(
     clippy::all,
+    dead_code,
     missing_docs,
     non_camel_case_types,
     non_upper_case_globals,