gpu: nova-core: vbios: remove unnecessary fields in PciRomHeader

gpu: nova-core: vbios: remove unnecessary fields in PciRomHeader

Remove unnecessary fields in PciRomHeader. This allows a simplification
to use `FromBytes` instead of reading fields piecemeal. A lot of these
checks were redundant as well since it checks the size of the `data`
first in `BiosImage`.

Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
Link: https://patch.msgid.link/20260525-fix-vbios-v5-18-e5e455251537@nvidia.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>