dmaengine: at_hdmac: set residue as total len in atc_tx_status

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

Idea from dw_dmac patch by Viresh Kumar.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>