This pass doesn't really do much now because nir_lower_vars_to_ssa can
already see through structures and considers them to be "split". This
pass exists to help other passes more easily see through structure
variables. If a back-end does implement arrays using scratch or
indirects on registers, having more smaller arrays is likely to have
better memory efficiency.
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
