rust: auxiliary: fix false positive warning for missing a safety comment

rust: auxiliary: fix false positive warning for missing a safety comment

Some older (yet supported) versions of clippy throw a false positive
warning for missing a safety comment when the safety comment is on a
multiline statement.

warning: unsafe block missing a safety comment
   --> rust/kernel/auxiliary.rs:351:22
    |
351 |                 Self(unsafe { NonNull::new_unchecked(adev) }),
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#undocumented_unsafe_blocks
    = note: requested on the command line with `-W clippy::undocumented-unsafe-blocks`

warning: 1 warning emitted

Fix this by placing the safety comment right on top of the same line
introducing the unsafe block.

Fixes: e4e679c8608e ("rust: auxiliary: unregister on parent device unbind")
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://patch.msgid.link/20251103203932.2361660-1-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>