i965/nir: use redundant phi optimization

Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>
Tested-by: Jason Ekstrand <jason.ekstrand@intel.com>
Signed-off-by: Connor Abbott <cwabbott0@gmail.com>

src/mesa/drivers/dri/i965/brw_fs_nir.cpp

@@ -52,6 +52,8 @@ nir_optimize(nir_shader *nir)
       nir_validate_shader(nir);
       progress |= nir_opt_constant_folding(nir);
       nir_validate_shader(nir);
+      progress |= nir_opt_remove_phis(nir);
+      nir_validate_shader(nir);
    } while (progress);
 }