gpu: nova-core: compute layout of the FRTS region

gpu: nova-core: compute layout of the FRTS region

FWSEC-FRTS is run with the desired address of the FRTS region as
parameter, which we need to compute depending on some hardware
parameters.

Do this in a `FbLayout` structure, that will be later extended to
describe more memory regions used to boot the GSP.

Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/r/20250619-nova-frts-v6-20-ecf41ef99252@nvidia.com
[ In doc-comment of FbLayout s/bootup process/boot process/ - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>