media: stm32-dcmi: fix DMA corruption when stopping streaming

commit b3ce6f6ff3c260ee53b0f2236e5fd950d46957da upstream.

Avoid call of dmaengine_terminate_all() between
dmaengine_prep_slave_single() and dmaengine_submit() by locking
the whole DMA submission sequence.

Signed-off-by: Hugues Fruchet <hugues.fruchet@st.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>