gpu: nova-core: Hopper/Blackwell: add FMC signature extraction

gpu: nova-core: Hopper/Blackwell: add FMC signature extraction

Extract the SHA-384 hash, RSA public key, and RSA signature from the
FMC ELF32 firmware sections. FSP Chain of Trust verification needs
these to validate the FMC image during boot.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Eliot Courtney <ecourtney@nvidia.com>
Link: https://patch.msgid.link/20260602032111.224790-14-jhubbard@nvidia.com
[acourbot: derive `Zeroable` on `FmcSignature` for in-place initialization]
Co-developed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>