gpu: nova-core: firmware: process Booter and patch its signature

gpu: nova-core: firmware: process Booter and patch its signature

The Booter signed firmware is an essential part of bringing up the GSP
on Turing and Ampere. It is loaded on the sec2 falcon core and is
responsible for loading and running the RISC-V GSP bootloader into the
GSP core.

Add support for parsing the Booter firmware loaded from userspace, patch
its signatures, and store it into a form that is ready to be loaded and
executed on the sec2 falcon.

Then, move the Booter instance from the `Firmware` struct to the
`start_gsp` method since it doesn't need to be kept after the GSP is
booted.

We do not run Booter yet, as its own payload (the GSP bootloader and
firmware image) still need to be prepared.

Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20250913-nova_firmware-v6-6-9007079548b0@nvidia.com
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>