dmaengine: rapidio: tsi721: Rename device_control

Rename the device_control callback of the TXX9 DMA driver to terminate_all
since it's all it's really doing. That will eventually be used to retrieve
slave capabilities.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>