rust: sync: atomic: separate import "blocks"

rust: sync: atomic: separate import "blocks"

Commit 14e9a18b07ec ("rust: sync: atomic: Make Atomic*Ops pub(crate)")
added a `pub(crate)` import in the same "block" as the `pub` one,
without running `rustfmt`, which would sort them differently.

Instead of running `rustfmt` as-is, add a newline to keep the import
"blocks" with different visibilities separate.

Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>