DMAENGINE: pch_dma: kill another usage of __raw_{read|write}l

Use {read|write}l instead of __raw_{read|write}l since PCH DMA
controller is PCI device.

Signed-off-by: Yong Wang <yong.y.wang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>