dw_dmac: autoconfigure data_width or get it via platform data

Not all of the controllers support the 64 bit data width. Make it configurable
via platform data. The driver will try to get a value from the component
parameters, otherwise it will use the platform data.

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@linux.intel.com>