gpu: nova-core: convert `/*` comments to `//`

The second form is preferred, and there was no reason to use the first.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/r/20250708-nova-docs-v4-4-9d188772c4c7@nvidia.com


Signed-off-by: Danilo Krummrich <dakr@kernel.org>