gpu: nova-core: factor .fwsignature* selection into a new find_gsp_sigs_section()

gpu: nova-core: factor .fwsignature* selection into a new find_gsp_sigs_section()

Keep Gsp::new() from getting too cluttered, by factoring out the
selection of .fwsignature* items. This will continue to grow as we add
GPUs.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patch.msgid.link/20260411024953.473149-2-jhubbard@nvidia.com
[acourbot: fix minor conflict.]
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>