AP_Param: show_all compiler error fix

libraries/AP_Param/AP_Param.cpp

@@ -2556,7 +2556,7 @@ void AP_Param::show_all(AP_HAL::BetterStream *port, bool showKeyValues)
          ap;
          ap=AP_Param::next_scalar(&token, &type)) {
         if (showKeyValues) {
-            port->printf("Key %i: Index %i: GroupElement %i  :  ", token.key, token.idx, token.group_element);
+            port->printf("Key %u: Index %u: GroupElement %u  :  ", (unsigned)token.key, (unsigned)token.idx, (unsigned)token.group_element);
         }
         show(ap, token, type, port);
         hal.scheduler->delay(1);