dw_dmac: print correct number of scanned descriptors

In case the first descriptor we found is available, the counter still remains 0
value which is wrong. This patch fixes the counter behaviour.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Viresh Kumar <viresh.linux@gmail.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>