ucc_geth: Implement Transmit on Demand support

Transmit on Demand: Fix spelling in config option, and make it actually enable TOD.

Signed-off-by: Michael Reiss <michael.f.reiss@freescale.com>
Signed-off-by: Michael Barkowski <michael.barkowski@freescale.com>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>