I'm going to take a different guess; I get a similar message. The motherboard has a Marvell disk controller in addition to the southbridge ports. When I boot without any drives attached to the Marvell controller, and the controller is enabled, I get a similar message. My board is an earlier Asus model.
Look in the BIOS for on-board components and disable the Marvell controller. If that makes the message go away, you can consider leaving it disabled until you need it.
If it can't be disabled in the BIOS and you are really, really curious, disconnect your HDD and connect it to the Marvell-controlled ports. If the message goes away, I was right.