dmaengine: dw: don't override platform data with autocfg

Let probe driver decide either it wants to auto configure the driver or have
explicitly defined properties.

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