It's a cosmetic bug in LLDP communications between the switch and the phone. It also occurs with many versions of Polycom phones. Verify that you don't see errors on the switch port in the form of incrementing runts, CRC, or collisions which would indicate an actual duplex issue.
The command "no lldp receive 802.3-info mac-phy-config" applied to the switch interfaces will stop the chatter permanently.
Typing "no events" will also suppress all terminal noise for the duration of a session. This includes this condition as well as T-1 errors, firewall events, etc.