I've just tested this in my lab using AP303H and it works using the same method as WLAN: just select the Centrailise-L2 DHCP scope in the wired profile and the traffic will go use the GRE tunnel.
But unfortunately my AP345s are being controlled by Airwave and there seems to be a bug in Airwave 8.2.7 because it doesn't present any dropdown menu for selecting DHCP policies when editing the Wired network profile IGC mode. See attached screenshot.