gpu: nova-core: introduce `bounded_enum` macro

gpu: nova-core: introduce `bounded_enum` macro

Introduce a powered-up version of our ad-hoc `impl_from_enum_to_u8`
macro that allows the definition of an enum type associated to a
`Bounded` of a given width, and provides the `From` and `TryFrom`
implementations required to use that enum as a register field member.

This allows us to generate the required conversion implementations for
using the kernel register macro and skip some tedious boilerplate.

Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patch.msgid.link/20260325-b4-nova-register-v4-1-bdf172f0f6ca@nvidia.com
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>