dmaengine: Add helper function to prep for error reporting

Dmaengine does not provide a way to pass back the result from a DMA
transaction through the callback function. We are adding dmaengine
helper function in order to prep for a mechanism that allow result
status and other information through the callback. The initial conversion
will make the existing driver use these new helper functions but retain
the original behavior of the code. However, the helper functions paves
a way towards adding the result parameter through callback.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>