rust: init: use explicit ABI to clean warning in future compilers

Starting with Rust 1.86.0 (currently in nightly, to be released on
2025-04-03), the `missing_abi` lint is warn-by-default [1]:

    error: extern declarations without an explicit ABI are deprecated
        --> rust/doctests_kernel_generated.rs:3158:1
         |
    3158 | extern {
         | ^^^^^^ help: explicitly specify the C ABI: `extern "C"`
         |
         = note: `-D missing-abi` implied by `-D warnings`
         = help: to override `-D warnings` add `#[allow(missing_abi)]`

Thus clean it up.

Cc: <stable@vger.kernel.org> # Needed in 6.12.y and 6.13.y only (Rust is pinned in older LTSs).
Fixes: 7f8977a7fe6d ("rust: init: add `{pin_}chain` functions to `{Pin}Init<T, E>`")
Link: https://github.com/rust-lang/rust/pull/132397 [1]
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Fiona Behrens <me@kloenk.dev>
Link: https://lore.kernel.org/r/20250121200934.222075-1-ojeda@kernel.org
[ Added 6.13.y to Cc: stable tag. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

0 files changed, 0 insertions, 0 deletions