dmaengine: dw-edma: fix __iomem type confusion

dmaengine: dw-edma: fix __iomem type confusion

The new driver mixes up dma_addr_t and __iomem pointers, which results
in warnings on some 32-bit architectures, like:

drivers/dma/dw-edma/dw-edma-v0-core.c: In function '__dw_regs':
drivers/dma/dw-edma/dw-edma-v0-core.c:28:9: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
  return (struct dw_edma_v0_regs __iomem *)dw->rg_region.vaddr;

Make it use __iomem pointers consistently here, and avoid using dma_addr_t
for __iomem tokens altogether.

A small complication here is the debugfs code, which passes an __iomem
token as the private data for debugfs files, requiring the use of
extra __force.

Fixes: 7e4b8a4fbe2c ("dmaengine: Add Synopsys eDMA IP version 0 support")
Link: https://lore.kernel.org/lkml/20190617131918.2518727-1-arnd@arndb.de/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20190722124457.1093886-2-arnd@arndb.de
Signed-off-by: Vinod Koul <vkoul@kernel.org>