dmaengine: dw-edma: Add HDMA DebugFS support

Add HDMA DebugFS support to show registers content

Signed-off-by: Cai Huoqing <cai.huoqing@linux.dev>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Tested-by: Serge Semin <fancer.lancer@gmail.com>
Link: https://lore.kernel.org/r/20230520050854.73160-5-cai.huoqing@linux.dev
Signed-off-by: Vinod Koul <vkoul@kernel.org>