nir: Count i/o slots correctly for per-view variables

This function wasn't counting driver slots correctly, resulting in
incorrect driver_location's and input_count. It seems intel doesn't use
this yet.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6514>
1 file changed