Even if it can be configured (I don't think it can), that's not a scenario we test in our QA efforts, so you're getting into uncharted waters.
In my experience very few organizations actually pull multiple ethernet segments to the same location, the vast majority of them accomplish the same effective things using VLANs.
Why were you considering this particular scenario?
Actually this can be done (if i understand you correctly)..
If you are looking to create two SSIDs (SSID-A and SSID-B) and have one be sent out Eth0 and one out Eth1
The first step in the process is configuring the AP’s second Ethernet port (eth1) with the proper VLAN Configuration. In this screenshot we have configured the second Ethernet port to have a native VLAN of 2.
After configuring eth1 with proper VLAN settings, we will want to configure the device level settings. This configuration is found under Optional Settings, Routing.
After configuring the device level configuration this is an example of a Network Configuration for the AP that would result in the original goal.
Hope this helps.
But: Be aware that all management traffic is always being sent out through the eth0 interface. This includes Radius servers for authentication. So if VLAN 2 needs Radius authentication, that server has to be reachable via eth0.