broadcom/vc5: Start using nir_opt_move_load_ubo().

In the absence of a general NIR or VIR-level scheduler, this at least
avoids spilling in
GTF-GLES3.gtf.GL3Tests.uniform_buffer_object.uniform_buffer_object_storage_layouts

src/broadcom/compiler/nir_to_vir.c

@@ -1202,6 +1202,8 @@ v3d_optimize_nir(struct nir_shader *s)
                 NIR_PASS(progress, s, nir_opt_constant_folding);
                 NIR_PASS(progress, s, nir_opt_undef);
         } while (progress);
+
+        NIR_PASS(progress, s, nir_opt_move_load_ubo);
 }
 
 static int