In descriptor mode, the descriptor running pointer is not maintained
by the interrupt handler, thus, driver finds the running descriptor
from the descriptor pointer field in the CHCRB register.
But, CHCRB::DPTR indicates *next* descriptor pointer, not current.
Thus, The residue calculation will be missed. This patch fixup it.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>