dmaengine/dw_dmac: set residue as total len in dwc_tx_status if status is !DMA_SUCCESS

If transfer status is !=DMA_SUCCESS, return total transfer len as residue,
instead of zero.

Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>