rust: drm: use new sync::aref path for imports
ARef and AlwaysRefCounted are being moved to sync::aref, and the
re-exports under types are planned to be removed. Thus, update imports
to the new path.
Acked-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260326-drm-rust-next-fix-aref-v1-2-7f6f58d2828a@google.com
Signed-off-by: Alice Ryhl <aliceryhl@google.com>