dmaengine: dw: substitute dma_read_byaddr by dma_readl_native

Since struct dw_dma is allocated and regs member is assigned properly we can
use standard IO accessors to the DMA registers.

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