nir: Actually propagate progress in nir_opt_move_load_ubo.

Found with Jasons new metadata rework (https://gitlab.freedesktop.org/mesa/mesa/merge_requests/950

).

Fixes: af355aaa "nir: add nir_opt_move_load_ubo() optimization pass"
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
(cherry picked from commit e24a7840)