dw_dmac: Move single descriptor from dwc->queue to dwc->active_list in dwc_complete_all

dwc_complete_all and other routines was removing all descriptors from dwc->queue
and pushing them to dwc->active_list. Only one was required to be removed. Also
we are calling dwc_dostart, once list is fixed.

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