ONE SPE is used for the Hypervisor so no hope of using it in the near future
Only a pretty good hack could disable the hypervisor totally and leave full acess to that SPE! But we already have enough for linux do you REALLY think you need it... I don't think that under linux are even available the full number of SPE's I think that only 4 are use din the current distributions (don't take my word for granted here)