dmaengine/dmatest: Terminate transfers on all channels in case of error or exit

In case, some error occurs while doing memcpy transfers, we must terminate all
transfers physically too. This is achieved by calling device_control() routine
with TERMINATE_ALL as parameter.

This is also required to be done in case module is removed while we are in
middle of some transfers.

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