dmaengine: add wrapper functions for device control functions

Add wrapper functions around the dma_device->device_control function
to bring back type safety. Also, add a wrapper function around
dma_async_tx_descriptor->tx_submit. This is named dmaengine_submit
instead of dmaengine_tx_submit to get rid of the confusing 'tx' in the
function name

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>