This is depend on how many AP managed by this controller & what is the total wireless traffic volume you may have. If you have more than 200+ AP (802.11n supports where single AP can give ~450 Mpbs max) & heavy use of wireless (ie video,heavy downloads through wireless), I would go ahead and bundle all 8 ports into single 8Gbps LAG.
Keep in mind, WLC does not support any etherchannel negotiation protocols (LACP or PAgP). So you have to configure "channel group mode on" command on switch side when port aggregating. Also unless you have 6500 pair of VSS, all physical ports from WLC LAG ports to be connected to same physical switch.
Here is the configuration guide reference for WLC 7.4.x software code