drm/nouveau: Remove DRM_NOUVEAU_GSP_DEFAULT config

drm/nouveau: Remove DRM_NOUVEAU_GSP_DEFAULT config

This option was originally intoduced because the GSP code path was
not well tested and we wanted to leave it up to distros which code path
they shipped by default. By now though, the GSP path is probably better
tested than the old firmware eg. Fedora ships GSP by default and we
generally run CTS on GSP. We've always been GSP-only on Ada and later.

So, this path removes the option and effectively sets the option to
always on. We still fall back to the old firmware if GSP is not found.
This change only affects Turing and Ampere.

Users can still set nouveau.config=NvGspRm=0 on the kernel command line
to force using the old firmware on Turing/Ampere.

Signed-off-by: Mel Henning <mhenning@darkrefraction.com>
Reviewed-by: Ben Skeggs <bskeggs@nvidia.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://lore.kernel.org/r/20250811213843.4294-2-mhenning@darkrefraction.com