gpu: nova-core: make Chipset::arch() const
We will use this method from const context.
Also take `self` by value since it is the size of a primitive type and
implements `Copy`.
Reviewed-by: Eliot Courtney <ecourtney@nvidia.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patch.msgid.link/20260306-turing_prep-v11-10-8f0042c5d026@nvidia.com
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>