Allow get_powerstat when rig is powered off

https://github.com/Hamlib/Hamlib/issues/1220

tests/rigctl_parse.c

@@ -1756,6 +1756,7 @@ readline_repeat:
                 && cmd_entry->cmd != 0x8f // dump_state
                 && cmd_entry->cmd != 0xf0 // chk_vfo
                 && cmd_entry->cmd != 0x87 // set_powerstat
+                && cmd_entry->cmd != 0x88 // get_powerstat
                 && cmd_entry->cmd != 0xa5 // client_version
                 && my_rig->caps->rig_model !=
                 RIG_MODEL_POWERSDR) // some rigs can do stuff when powered off