nir/lower_io_arrays: Fix xfb_offset bug

I noticed this once I started gathering xfb_info after
nir_lower_io_arrays_to_elements_no_indirect.

Fixes: b2bbd978d0b ("nir: fix lowering arrays to elements for XFB outputs")
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