v5x: use low bandwidth mavlink mode

This changes the default mavlink message set from onboard to
onboard_low_bandwidth, which drastically reduces the bandwidth required to get a
usable connection.

src/modules/mavlink/module.yaml

@@ -59,6 +59,7 @@ parameters:
                 8: External Vision
                 #9: External Vision Minimal # hidden
                 10: Gimbal
+                11: Onboard Low Bandwidth
             reboot_required: true
             num_instances: *max_num_config_instances
             default: [0, 2, 0]