dmaengine: hsu: correct residue calculation of active descriptor

dmaengine: hsu: correct residue calculation of active descriptor

commit a197f3c7d48c0c1f45076ea47533a76ba9b1a959 upstream.

The commit f0579c8ceaf1 ("dmaengine: hsu: speed up residue calculation")
speeded up calculation of the queued descriptor but broke the initial residue
value for active descriptor.

In accordance with documentation the hardware descriptor is updated each time
DMA transfered some bytes. It means we have to calculate a sum of lengths of
non-submitted hardware descriptors and whatever current values in the hardware.
Do this straightforward.

Fixes: f0579c8ceaf1 ("dmaengine: hsu: speed up residue calculation")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>