dmaengine: shdma: extend .device_terminate_all() to record partial transfer

This patch extends the .device_terminate_all() method of the shdma driver
to return number of bytes transfered in the current descriptor.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>