gpu: nova-core: firmware: process the GSP bootloader

The GSP bootloader is a small RISC-V firmware that is loaded by Booter
onto the GSP core and is in charge of loading, validating, and starting
the actual GSP firmware.

It is a regular binary firmware file containing a specific header.
Create a type holding the DMA-mapped firmware as well as useful
information extracted from the header, and hook it into our firmware
structure for later use.

The GSP bootloader is stored into the `GspFirmware` structure, since it
is part of the GSP firmware package. This makes the `Firmware` structure
empty, so remove it.

Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20250913-nova_firmware-v6-8-9007079548b0@nvidia.com


Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>