rc_update_params: clarify failsafe channel and threshold
rc_update_params: clarify failsafe channel and threshold

acfloria/Firmware,krbeverx/Firmware,acfloria/Firmware,acfloria/Firmware,acfloria/Firmware,krbeverx/Firmware,krbeverx/Firmware,krbeverx/Firmware,acfloria/Firmware,krbeverx/Firmware,krbeverx/Firmware,krbeverx/Firmware,acfloria/Firmware,acfloria/Firmware