nir: allow opt_peephole_select to handle nir_instr_type_deref

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/compiler/nir/nir_opt_peephole_select.c

@@ -89,6 +89,7 @@ block_check_for_allowed_instrs(nir_block *block, unsigned *count, bool alu_ok)
          break;
       }
 
+      case nir_instr_type_deref:
       case nir_instr_type_load_const:
          break;