gpu: nova-core: make formatting compatible with rust tree

gpu: nova-core: make formatting compatible with rust tree

Commit 38b7cc448a5b ("gpu: nova-core: implement Display for Spec") in
drm-rust-next introduced some usage of the Display trait, but the
Display trait is being modified in the rust tree this cycle. Thus, to
avoid conflicts with the Rust tree, tweak how the formatting machinery
is used in a way where it works both with and without the changes in the
Rust tree.

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://patch.msgid.link/20251117-nova-fmt-rust-v1-1-651ca28cd98f@google.com
Signed-off-by: Alice Ryhl <aliceryhl@google.com>