rust: std_vendor: simplify `{ .. macro! .. }` with inner attributes

rust: std_vendor: simplify `{ .. macro! .. }` with inner attributes

It is cleaner to have a single inner attribute rather than needing
several hidden lines to wrap the macro invocations.

Thus simplify them.

Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Tested-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://lore.kernel.org/r/20240904204347.168520-20-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>