dmaengine: Make an order in struct dma_device definition

Make an order in struct dma_device:
- added missing kernel doc descriptions
- put descriptions in the order of appearance in the code
- updated indentation where it makes sense

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230130110503.52250-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>