gpu: nova-core: firmware: parse `FalconUCodeDescV2` via `zerocopy`

gpu: nova-core: firmware: parse `FalconUCodeDescV2` via `zerocopy`

Now that we have `zerocopy` support, we can avoid some `unsafe` code.

For instance, for `FalconUCodeDescV2`, we can replace the `unsafe impl
FromBytes` by safely deriving `zerocopy`'s `FromBytes` and then calling
`read_from_prefix`.

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patch.msgid.link/20260608141439.182634-20-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>