doc:dmaengine: clarify DMA desc. pointer after submission

[Federico Vaga <federico.vaga@cern.ch>]

On Monday, February 11, 2019 12:54:11 PM CET Vinod Koul wrote:
> On 08-02-19, 16:30, Federico Vaga wrote:
> > It clarifies that the DMA description pointer returned by
> > `dmaengine_prep_*` function should not be used after submission.
> > 
> > Signed-off-by: Federico Vaga <federico.vaga@cern.ch>
> > ---
> > 
> >  Documentation/driver-api/dmaengine/client.rst | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/Documentation/driver-api/dmaengine/client.rst
> > b/Documentation/driver-api/dmaengine/client.rst index
> > fbbb2831f29f..d728e50105eb 100644
> > --- a/Documentation/driver-api/dmaengine/client.rst
> > +++ b/Documentation/driver-api/dmaengine/client.rst
> > 
> > @@ -168,6 +168,13 @@ The details of these operations are:
> >     dmaengine_submit() will not start the DMA operation, it merely adds
> >     it to the pending queue. For this, see step 5,
> >     dma_async_issue_pending.
> > 
> > +   .. note::
> > +
> > +      After calling ``dmaengine_submit()`` the submitted transfer
> > descriptor +      (``struct dma_async_tx_descriptor``) belongs to the DMA
> > engine. +      Consequentially, the client must consider invalid the
> > pointer to that
> Consequently

I'm not a native speaker but consequentially and consequently should be 
synonymous. As fa as I understood. but I do not mind to change it if you think 
is better.

> > +      descriptor.
> > +
> 
> Applied after fixing the typo and added tag as Documentation: dmaengine...

I used doc to make the string shorter

> 
> >  5. Issue pending DMA requests and wait for callback notification
> >  
> >     The transactions in the pending queue can be activated by calling the