dmaengine: dw-edma: Change rg_region to reg_base in struct dw_edma_chip

struct dw_edma_region rg_region included virtual address, physical address
and size information. But only the virtual address is used by EDMA driver.
Change it to void __iomem *reg_base to clean up code.

Link: https://lore.kernel.org/r/20220524152159.2370739-4-Frank.Li@nxp.com


Tested-by: Serge Semin <fancer.lancer@gmail.com>
Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Acked-By: Vinod Koul <vkoul@kernel.org>