drm/nouveau/gsp: split device handling out on its own

Split handling of NV01_DEVICE (and other related objects) out into its
own module.

Aside from moving the function pointers, no code change is intended.

Signed-off-by: Ben Skeggs <bskeggs@nvidia.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Timur Tabi <ttabi@nvidia.com>
Tested-by: Timur Tabi <ttabi@nvidia.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>